单项选择题

Questions 19 to 22 are based on the conversation you have just heard.

A．The high temperatures required for its use.
B．The lack of trained environmental engineers.
C．The opposition of automobile manufacturers.
D．The high cost of materials used in its production.
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填空题
The unemployed men were ashamed of being unemployed because they had the opinion that ______.
单项选择题
A．Man will probably be able to live there in 200 years.B．Scientists are rather pessimistic about it.C．Man will probably be able to live there in 100,000 years’ time.D．Scientists are optimistic about overcoming the difficulties soon.
A．Man will probably be able to live there in 200 years.
B．Scientists are rather pessimistic about it.
C．Man will probably be able to live there in 100,000 years’ time.
D．Scientists are optimistic about overcoming the difficulties soon.
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