单项选择题

It can be inferred form the passage that ______.

A． there was once a wave of Mars exploration by scientists.
B． life has existed on Mars.
C． Lowell's claim is proved incorrect today.
D． It's a waste of time to try to answer the question concerning life on Mars.

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单项选择题

Which of the following statements about electronic ink is true

A． The electronic book is now available for $ 200,400.
B． The ink has already been produced a great deal.
C． The ink will work only with something conductive.
D． The ink will make an electronic book unaffordable.

单项选择题

Which statement is NOT true according to this article

A． Energy will be expensive and in short supply.
B． There will be more cars than ever in 1997.
C． The air will be cleaner in 1997.
D． People will walk everywhere instead of going by cars.