1.He told me the secret in a low ( )

He hold me the secret in a low voice
in a low voice
低声地
固定搭配
The little girl went out without sayinig anything
saying 为动名词,签名应该有介词.without saying anything啥也没说,符合句意.
Schools need help with talking care of children while parents are working.
while为连词,are working做并列句.讲笑话,听的人肯定不会哭吧?
Mary was heard to laugh just now .What happend?John was telling a joke.
hear someone to do/doing 为固定搭配,此处为被动式.

上面回答很详细了。

1.B 2.without,根据意思可知道是小女孩什么都没说就出去了。3.are working,while后面基本都是ing形式4.D被动还原to

1. B voice 指的是人的声音
2. without
3. are working 强调正在进行的动作
4.D 讲笑话意味着是笑。be heard to do sth