单项选择题

Training astronauts（）not an easy thing.

A．are
B．is
C．were
D．be

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单项选择题

After the new technique was introduced, the factory produced（）tractors in 1988 as the year before.

A．as twice many
B．as many twice
C．twice as many
D．twice many as

单项选择题

Before setting out on a long journey, you must make sure that your car is（）

A．in place
B．in order
C．in practice
D．in theory

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