[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.

[单项选择]This may have preserved the elephant from being wiped out as well as other animals ______ in Africa.
A. hunted
B. hunting
C. that hunted
D. are hunted

[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]What distinguishes morphology from syntax deals with the rules governing the combination of

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

[填空题]Why must we pay taxes The answer is that the government needs money for many things, for example, to pay its soldiers, sailors and airmen, to build roads, bridges, offices, schools, etc, and to buy goods from abroad ; and only the people of the country can supply the money. One of the most important taxes is income-tax which a person pays according to the amount of his income, whether he is a merchant, a doctor, a lawyer, a shopkeeper, a miner or anything else. This is called a "direct" tax, because it is paid in money directly to the government. Another tax is paid on goods such as watches, jewelry, new clothes, tobacco, wine, etc, when they are brought into a country. Such a tax is paid as part of the price of these goods if they are late sold in shops. We call it "indirect" tax, because it is paid indirectly through the shopkeepers. People usually complain about having to pay taxes, but they forget that the money is spent on things that they and their families need. We need policeme