The children very quiet；I wonder what they up to.A. were； are beingB. are being；areC. a

问题补充：

The children very quiet；I wonder what they up to.

A. were； are being

B. are being；are

C. are；do

D. are being；do

答案：

A. were； are being

(答案→)B. are being；are

C. are；do

D. are being；do

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