I had just started back for the house to change my clothes ________I heard voices.

A．as

B．when

C．after

D．while

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参考答案

连词as和after分别意为“随着，因为”和“在……之后”，与句意逻辑不符。whi1e多用于延续性或同时性动作，但此句的主句与从句相关的动作分别为start与hear，均为短暂性动作，所以应当用when。

1 It seems oil________ from this pipe for some time. We '11 have to take the machine apart to put it right.

A．had leaked

B．is leaking

C．leaked

D．has been leaking

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2 When he arrived, he found ________ the aged and the sick at home.

A．none but

B．none other than

C．nothing but

D．no other than

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3 The pressure ________causes American to be energetic, but it also puts them trader a constant emotional strain.

A．to compete

B．competing

C．to be competed

D．having competed

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