At last she left her house and got to the airport, only_

单选题 At last she left her house and got to the airport, only__ the plane flying away．

A．having seen
B．to have seen
C．to see
D．saw

参考答案C

解析: C。最终她离开了家赶到机场，但是只见到飞机飞走了。
考查非谓语动词。此处表示意外的结果，需使用动词不定式作结果状语，不用分词。

单选题 A large fish was slowly swimming through the water, its tail __ back and forth like the pendulum of a clock．

A．swung
B．was swinging
C．was swung
D．swinging

单选题 They are teachers and don't realize __ to start and run a company．

A．what it takes
B．what takes it
C．what they take
D．what takes them

单选题 The millions of calculations involved, __ by hand, would have lost all practical value by the time they were finished．

A． had they been done
B．having been done
C．they had been done
D．they were done