There are many kinds of birds in Australia, and over 140 species of snakes, many of ________ are extremely dangerous．

A．them

B．which

C．what

D．those

Private cars are required to turns off roads one out of five weekdays ________ the traffic pressure．

A．to reduce

B．reducing

C．reduce

D．reduced

There is a saying ________ swimming is a good way to keep fit．

A．which

B．what

C．that

D．where

This is a city which lives for today while ________ by its past．

A．surround

B．surrounding

C．surrounded

D．to surround

In September 2008, China’s key milestone in space travel ________ when Zhai Zhigang conducted the first space walk．

A．reached

B．was reached

C．has reached

D．had been reached

We ________ last night, but we went to appreciate the flowerbeds and streetlights in Tiananmen Square instead．

A．might study

B．could study

C．should have studied

D．must have studied

Each of us, ________ old or young, is a valuable member of society．

A．however

B．whenever

C．whoever

D．whatever

If a computer crashes, you will lose the file you ________ on unless you save it regularly．

A．are working

B．work

C．will work

D．worked

There you can see beautiful tall buildings on ________ side of the square．

A．all

B．either

C．both

D．every

We spent 16 glorious days in August ________ the athletes’ joys and tears, and we were amazed at their ability．

A．shared

B．to share

C．sharing

D．share