She wonders why no one a___the telephone now.只有一个空,有now不是应该用is answering

题目

She wonders why no one a___the telephone now.只有一个空,有now不是应该用is answering

答案

这是非谓语动词的知识（一个句子里面只能有一套主谓宾,从句除外,Wonder已经是一个动词了,你要再来个is这句话就两个动词了,不符合句子要求）
这是现在分词表示状态,换句话说就是现在分词表主动,不是现在进行时.
举个例子吧,比如说
She came into the classroom wearing a hat.她进到教室来,带着眼镜.
而不是She came into the classroom is wearing a hat.
上面是现在分词表主动.
如果是被动的话,就要用过去分词
比如说
She came into the classroom followed by a dog.
她进到教室来,被一只狗跟着.