问题
选择题
If he is once ______ laughing, he finds ______ difficult to stop.
A．set about; that
B．set out; this
C．set force; which
D．set off; it
答案
答案：D
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If he is once ______ laughing, he finds ______ difficult to stop.
A．set about; that
B．set out; this
C．set force; which
D．set off; it
答案：D