When he heard the joke,he couldn't help___(laugh)(请写出原因,
问题描述：
When he heard the joke,he couldn't help___(laugh)
(请写出原因,
答
laughing
couldn't help后面接动词+ing形式．
他一听到那个笑话，就不住的笑了出来．
望采纳
答
用laughing
can not doing;是禁不住做媒事。
如用to do 是不能帮忙做媒事
答
答案是;laughing
couldn't help donging是一个固定词组,意思是情不自禁做某事
比如：couldn't help crying的意思是情不自禁的哭了
答
laughing
couldn't help后面是要接动词的ing形式的．
翻译：他一听到那个笑话，就禁不住笑了出来．