I couldn't help when I heard the joke.A. being laughedB. laughingC. to be laughingD. to l

问题补充：

I couldn help when I heard the joke.

A. being laughed

B. laughing

C. to be laughing

D. to laugh

答案：

A. being laughed

(答案→)B. laughing

C. to be laughing

D. to laugh

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