[填空题]We must derive hydrogen from ____________ with a view to a pure hydrogen economy.

[填空题]We must derive hydrogen from renewable sources with a view to a pure hydrogen economy.

[填空题]We must derive hydrogen from ____________ with a view to a pure hydrogen economy.

[填空题]We must derive hydrogen from __________________ with a view to a pure hydrogen, economy.

[填空题]How many steps must we take when we read a map
We have to take （）.

[填空题]

How many steps must we take when we read a map We have to take ______.

[填空题]How many steps must we take when we read a map
We have to take ______.

[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。 D. 我们必须竭尽所能使贫困国家的部分地区脱贫。

[单项选择]We must make sure we get to the station（），because we’ve still got to buy our tickets.
A. on time
B. in good time
C. for a time
D. at one time

[填空题]We regret that we must advise you to regard their request for credit in caution.

[填空题]When we compare men with animals, we must remember that a man is also an animal. But in making this comparison, it is sometimes more convenient to refer to the rest of the animal kingdom as "animals".
(1) .
Many animals are intelligent in the sense that they can explore their surroundings or acquire new skills by learning from their parents. Animal organisms have organs whose physical power exceeds the power of men. The bodies of men have no wings and cannot fly. Men cannot imitate fish and spend long periods under water unless they carry breathing apparatus with them.
(2) . But it is very uncommon for animals to go mad or destroy their own kind. Animals, left to themselves, do not disturb the balance of nature. They do not turn grassland into desert or make water undrinkable by filling whole lakes and rivers with waste materials. Compared with most other organisms—if we see him as a part of nature—man is wasteful and destructive. Though he is more intell