题目内容：

When Jane fell off the bike,the other children ___.
A.were not able to help laughter
B.could not help but laughing
C.could not help laughing
D.could not help to laugh

优质解答

C. could not help laughing.第一句不对因为help 和laugh 都是动作动词（action verb)第二句不对因为but是个clause,需要一个动词（laugh）,而laughing是一个participle. Participles是通常当gerunds或者modifiers用....