15．It's guessed the victim by a knife．【查看更多】

阅读理解。

    David's got a text message from his friend Sam. Can you understand it?
    7,15    20,15   20,8,5      16,1,18,11
    This message was in code (密码, 代码). How many letters are there in the English alphabet?
Twenty-six. So can you read it now?

A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	...
1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	...

David decided to use a different code in his answer to Sam. This time, he was putting A instead of B,
B instead of C, and so on. His message to Sam shown on the right was very short. Can you understand?

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

A

    Sam guessed David's code, and he replied: ZESDQ, RBGNNK. When David's little sister saw the message,
she felt puzzled. She couldn't read it at all. But David was very happy that his sister couldn't read his message!
   Lots of people use codes to send secret messages. In a war, secrets are very important so soldiers often
send each other messages in code. Nowadays, we can use computers to make and break difficult codes. Even
before computers, people invented other machines to do this.
    Here's a famous machine that Germans used in the Second World War (1941-1945). It's called the Enigma
Machine. The machines were very big, heavy and expensive. Every day they changed the codes automatically,
and this made it almost impossible for anyone to break the codes. The person sending a message had one
machine, and the person receiving the message had another.

1．Sam asked David to go to the ______.

[ ]

A．park
B．house
C．museum
D．zoo

2．Sam told David to meet him ______.

[ ]

A．before breakfast
B．after school
C．after dinner
D．before school

3．Codes are used to keep something ______.

[ ]

A．new
B．old
C．secret
D．known

4．People will never know the meaning if they can't ______ the code.

[ ]

A．break
B．make
C．change
D．write

5．The best title of this passage is .

[ ]

A．English Letters
B．Codes
C．Messages
D．Machines

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Look at that red car! I think it’s in the world.

A．more beautiful B．so beautiful C．the most beautiful D．such beautiful

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It's time________the meeting．

A.
to
B.
of
C.
for
D.
with

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—Who is the little girl in the picture?

—It's me. The picture __________10 years ago.

A. took B. is taken C. has taken D. was taken

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What is the sky(天空)? Where is it? How high is it? What lies above it? These questions are hard to answer, aren’t they?
Is the sky blue? The sky has no color. We know that there is air around the world. When planes fly, they need air to lift their wings(翼) . Planes cannot fly very high because when they go high, the air gets thinner. If we go up about 1,200 kilometers from the earth, we find there is no air.
Perhaps(也许) we can answer some of our questions now. The sky is space(空间). In this space there is only the sun, the moon and all the stars.
6.What is the sky?
A. It’s the clouds       B. It’s space.     C It’s air      D It’s nothing
7. The sky _____
A. is blue        B. is white        C. is black     D. has no color
8. Planes cannot fly very high because _________.
A. the air becomes thinner                         B. the flying machine is not good
C. people will be afraid if the planes fly too high      D. it is not necessary for planes to fly so high
9 If we go up about 1,200 kilometers from the earth, we find ___________.
A. there is more air   B. there is less air   C .there is nothing but air   D there is no air
10. In space there is _________.
A. nothing       B. air everywhere       C. everything       D. only the sun , the moon and all the stars

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It's time________the meeting．