14 years ago, the nine million citizens of London heard sirens(警报)all over the town. Emergency services, the fire brigade, the ___1___, hospitals and ambulances stood by, ready to go ___2___ action. In railway and underground stations, people ___3___ posters and maps telling them ___4___ to go and what to do in the emergency. This was ___5___ Flood-call. London wasn’t flooded yet. But it is ___6___ that it will be. In 1236 and 1663．London was badly flooded．In1928, many people ___7___ in Westminster, the heart of ___8___ , frowned in floods. And in 1953, 100 people living on the eastern edge of the London suburbs were___9___ again in the floods.___10___, the Greater London council(会议) is taking action to ___11___ this terrible accident happening again. ___12___ the flood wall will not be built until the 1980s. And in the meantime, Londoners ___13___ be prepared．When it ___14___, 50 underground stations will be ___15___ water. Electricity, gas and phone services will be out of ___16___.  Roads will be impossible. It will be impossible to___17___ any of the bridges between North and South London.  Imagine—London ,will ___18___ like Venice.

　　  But the Flood-call didn’t ___19___ panic(惊慌) among Londoners. Most people knew it was just a___20___ One comment from a lady who was walking along the Embankment when the sirens sounded was,“It’s a flood warning, isn’t it? The water doesn’t lock high tome.”

1．A．Londoners

B．police

C．doctors

D．nurses

2．A．up

B．into

C．to

D．it

3．A．saw

B．put up

C．received

D．read

4．A．when

B．what

C．where

D．why

5．A．Exercise

B．Train

C．Drill

D．practice

6．A．impossible

B．necessary

C．possible

D．unnecessary

7．A, living

B．staying

C．lived

D．stayed

8．A．England

B．Europe

C．London

D．world

9．A．saved

B．killed

C．in danger

D．safe

10．A．Then

B．Later

C．At last

D．In the future

11．A．prevent

B．make

C．help

D．control

12．A．And

B．Now

C．So

D．But

13．A．would

B．must

C．could

D．ought

14．A．starts

B．begins

C．happens

D．takes place

15．A．below

B．above

C．under

D．in

16．A．water

B．city

C．action

D．houses

17．A．cross

B．across

C．pass

D．past

18．A．look

B．sound

C．see

D．hear

19．A．take

B．get

C．cause

D．make

20．A．proposal

B．warning

C．joke

D．game

　　  But the Flood-call didn’t ___19___ panic(惊慌) among Londoners. Most people knew it was just a___20___ One comment from a lady who was walking along the Embankment when the sirens sounded was,“It’s a flood warning, isn’t it? The water doesn’t lock high tome.”

1．A．Londoners

B．police

C．doctors

D．nurses

2．A．up

B．into

C．to

D．it

3．A．saw

B．put up

C．received

D．read

4．A．when

B．what

C．where

D．why

5．A．Exercise

B．Train

C．Drill

D．practice

6．A．impossible

B．necessary

C．possible

D．unnecessary

7．A, living

B．staying

C．lived

D．stayed

8．A．England

B．Europe

C．London

D．world

9．A．saved

B．killed

C．in danger

D．safe

10．A．Then

B．Later

C．At last

D．In the future

11．A．prevent

B．make

C．help

D．control

12．A．And

B．Now

C．So

D．But

13．A．would

B．must

C．could

D．ought

14．A．starts

B．begins

C．happens

D．takes place

15．A．below

B．above

C．under

D．in

16．A．water

B．city

C．action

D．houses

17．A．cross

B．across

C．pass

D．past

18．A．look

B．sound

C．see

D．hear

19．A．take

B．get

C．cause

D．make

20．A．proposal

B．warning

C．joke

D．game

Did you ever wonder why leaves change colors in autumn, or how it happens? Here’s a quick explanation.
First of all, you’ve probably noticed that not all trees lose their leaves. There are two major types of trees: deciduous trees and evergreens. Evergreens keep their leaves and stay green all year long. The deciduous trees are the ones that lose their leaves each year.
In autumn, the days begin to get shorter. The sun is also lower in the sky at noon, which causes temperatures to be cooler. The combination of less sunshine and lower temperatures is what causes the deciduous trees to drop their leaves. In winter, deciduous trees “go to sleep”, sort of like a bear goes into hibernation.
Leaves are the food factories for a plant. Unlike animals，plants make their own food by taking energy directly from the sun. Plants do this by using a chemical in their leaves called chlorophyll.
Chlorophyll is green. During the spring and summer the leaves of a deciduous tree look green because there is a lot of chlorophyll there. In autumn, however, the sunshine becomes more  scarce and the leaves on the trees stop making new chlorophyll. As the old chlorophyll starts to break down, the green color of the leaf begins to go away.
You’ve probably also noticed that the leaves of different kinds of trees change different colors. The leaves of some trees turn yellow or orange, while the leaves of other trees turn bright red or purple. The different colors are caused by the different chemical reactions that are happening in the leaves.
For example, the leaves of some trees turn yellow when the chlorophyll breaks down. When the green chlorophyll goes away, a yellow pigment in the leaf becomes visible. The yellow pigment, called cartenoid, was already there during the summer, but is was not easily seen because there was too much green chlorophyll.
In other trees where the leaves turn red or purple a different chemical reaction takes place. In those leaves the chlorophyll also breaks down, but another chemical reaction takes place at the same time. Chemicals in the leaves, called starches, begin to change into chemicals called anthocyanins, which give the leaves their red and purple colors.
So next time you see the beautiful colors of autumn you will also know the science behind that beauty.
46.   What is the correct term for trees that lose their leaves in the autumn?
A. Evergreens       B. Deciduous        C. Cartenoids  D. Anthocyanins
47.   Which of the following is NOT mentioned as a cause of trees dropping their leaves?
A. A change in temperature   B. The amount of daylight available
C. Extra chlorophyll         D. Chemical changes in the leaves
48.   If there are 50 evergreens and 10 deciduous trees in a forest, in autumn what color are most of the leaves in the forest likely to be?
A. Green B. Red and purple
C. Yellow        D. not enough information to determine the answer
49.   Which of the following is only present in leaves during the autumn?
A. Chlorophyll       B. Starch C. Cartenoids        D. Anthocyanins
50.   Where would such an article mostly likely be published?
A. In a book                   B. In a primary school science text book
C. In a magazine for young people       D. All are equally likely

Did you ever wonder why leaves change colors in autumn, or how it happens? Here’s a quick explanation.

First of all, you’ve probably noticed that not all trees lose their leaves. There are two major types of trees: deciduous trees and evergreens. Evergreens keep their leaves and stay green all year long. The deciduous trees are the ones that lose their leaves each year.

     In autumn, the days begin to get shorter. The sun is also lower in the sky at noon, which causes temperatures to be cooler. The combination of less sunshine and lower temperatures is what causes the deciduous trees to drop their leaves. In winter, deciduous trees “go to sleep”, sort of like a bear goes into hibernation.

Leaves are the food factories for a plant. Unlike animals，plants make their own food by taking energy directly from the sun. Plants do this by using a chemical in their leaves called chlorophyll.

Chlorophyll is green. During the spring and summer the leaves of a deciduous tree look green because there is a lot of chlorophyll there. In autumn, however, the sunshine becomes more  scarce and the leaves on the trees stop making new chlorophyll. As the old chlorophyll starts to break down, the green color of the leaf begins to go away.

You’ve probably also noticed that the leaves of different kinds of trees change different colors. The leaves of some trees turn yellow or orange, while the leaves of other trees turn bright red or purple. The different colors are caused by the different chemical reactions that are happening in the leaves.

For example, the leaves of some trees turn yellow when the chlorophyll breaks down. When the green chlorophyll goes away, a yellow pigment in the leaf becomes visible. The yellow pigment, called cartenoid, was already there during the summer, but is was not easily seen because there was too much green chlorophyll.

In other trees where the leaves turn red or purple a different chemical reaction takes place. In those leaves the chlorophyll also breaks down, but another chemical reaction takes place at the same time. Chemicals in the leaves, called starches, begin to change into chemicals called anthocyanins, which give the leaves their red and purple colors.

So next time you see the beautiful colors of autumn you will also know the science behind that beauty.

46.   What is the correct term for trees that lose their leaves in the autumn?

A. Evergreens       B. Deciduous        C. Cartenoids  D. Anthocyanins

47.   Which of the following is NOT mentioned as a cause of trees dropping their leaves?

A. A change in temperature   B. The amount of daylight available

C. Extra chlorophyll          D. Chemical changes in the leaves

48.   If there are 50 evergreens and 10 deciduous trees in a forest, in autumn what color are most of the leaves in the forest likely to be?

A. Green B. Red and purple

C. Yellow         D. not enough information to determine the answer

49.   Which of the following is only present in leaves during the autumn?

A. Chlorophyll       B. Starch C. Cartenoids        D. Anthocyanins

50.   Where would such an article mostly likely be published?

A. In a book                    B. In a primary school science text book

C. In a magazine for young people       D. All are equally likely

完形填空

　14 years ago, the nine million citizens of London heard sirens(警报) all over the town．Emergency（紧急）services, the fire brigade, the 　1　 , hospitals and ambulances（救护车）stood by ready to go 　2　　 　action．In railway and underground stations, people 　3　　 　posters and maps telling them 　4　　 　to go and what to do in the emergency．This was 　5　　 　Floodcall．London wasn't flooded 　6　　 　．But it is 　7　　 　that it will be．

　In 1236 and 1663, London 　8　　 　．In 1928 many people 　9　　 　in Westminster, the heart of 　10　　 　, drowned (淹死) in floods．And in 1953, 100 people living on the eastern edge of the London suburbs(郊区)were 　11　　 　again in the floods． 　12 　, the Greater London Council（会议）is taking action to 　13　　 　this terrible accident happening again． 　14 　the flood wall will not be built 　15　　 　the 1980s．And in the meantime, Londoners 　16　　 　be prepared．When it 　17　　 　, 50 undergound stations will be 　18　　 　water．Electricity, gas and phone services will be out of 　19　　 　．Roads will be impossible．It will be impossible to 　20　　 　any of the bridges between North 　21　　 　South London．Imagine London will 　　 22　　 like Venice(威尼斯)．

　But the floodcall didn't 　23　　 　panic (惊慌) among Londoners．Most people knew it was just a 　24　　 　．One comment from a lady who was walking along the Embankment when the sirens sounded was, “It's a flood warning, isn't it? The water doesn't look 　25　　 　me．”