29. He was busy preparing a speech only once in a while to rise from the table for a te

问题补充：

29. He was busy preparing a speech , only once in a while to rise from the table for a tea .

A. stopping

B. to stop

C. to have stopped

D. having stopped

答案：

(答案→)A. stopping

B. to stop

C. to have stopped

D. having stopped

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