Tom is doing his homework.变成否定句怎么变?
问题描述：
Tom is doing his homework.变成否定句怎么变?
答
Tom is not doing his homework. 句子中的动词是be 动词的话，就直接在动词后加not 否定就好了。
答
有情态动词的，有系动词的在其后直接加not，没有系动词的要在动词后借助动词don't,didn't或doesn't.
补充：系动词包括1be动词(am,is,are)，2感官动词（feel,smell,taste......）3表示转换的词语（turn,become,come,grow......）
根据Tom is doing his homework可知is是系动词，所以要改为：
Tom isn't doing his homework
希望能帮助你！
答
Tom is not doing his homework