[单项选择]We must （　）on water during the dry season.
A. economical
B. economize
C. economy
D. economically

[单项选择]We must （　） on water during the dry season.
A. economical
B. economize
C. economy
D. economically

[单项选择]How many gallons of water must be mixed with 1 gallon of a 15-percent salt solution to obtain a 10-percent salt solution ？（）
A. 0.50
B. 0.67
C. 1.00
D. 1.50
E. 2.00

[单项选择]It was during summer breaks that we first taste the satisfaction that work ______ into hard currency.
A. translates
B. transfers
C. transplants
D. transmits

[单项选择]We must do away with the water pollution ______ with the growth offish.
A. interferes
B. interfering
C. interfered
D. being interfered

[单项选择]______ around the Water Cube, we were then taken to see the Bird's Nest for the 2008 Olympic Games.
A. Having shown
B. To be shown
C. Having been shown
D. To show

[单项选择]We must do whatever we can to free some parts of the country from poverty（）
A. 我们必须做任何事情，我们就可以使贫困的国家部分免费。
B. 我们必须竭尽所能，使贫困的国家部分免费。
C. 我们必须竭尽所能消除国内某些地区的贫困。

[单项选择]Batteries must be kept in dry places in case electricity should leak away.（）
A. 电池应该放在干燥的地方，以防漏电。
B. 电池放在干燥的地方，才会漏电。
C. 电池必须放在干燥的地方，这样的话电会漏掉。
D. 电池应该放在通风的地方，以防电泄漏。

[单项选择]（）we need air and water, so do we need criticism and self-criticism.
A. Even though
B. So long as
C. Just as
D. Now that

[单项选择]First and foremost, we must work out how we are going to get there.
A. think
B. plan
C. write
D. check

[单项选择]

During recent years we have heard much about "race": how this race does certain things and that race believes certain things and so on. Yet, the (21) phenomenon of race consists of a few surface indications.
We judge race usually (22) the coloring of the skin: a white race, a brown race, a yellow race and a black race. But (23) you were to remove the skin you could not (24) anything about the race to which the individual belonged. There is (25) in physical structure, the brain or the internal organs to (26) a difference.
There are four types of blood. (27) types are found in every race, and no type is distinct to any race. Human brains are the (28) . No scientists could examine a brain and tell you the race to which the individual belonged. Brains will (29) in size, but this occurs within every race. (30) does size have anything to do with intelligence. The largest brain (31) ex
A. All
B. Most
C. No
D. Some