例:write为原形 一般现在时:He writes his paper. 肯定句:He wrote his paper.(把动词原形变为过去式即可) He is writing his paper.[把动词原形变为be(注意人称am,is,are)+v.-ing] 改为: 否定句:He didn't write his paper.(可以理解为把过去式“转移”到助动词上变为didn't,动词则变回原形) He isn't writing his paper.(可以理解为直接be动词后加not,即为否定形式) 一般疑问句: Did he write his paper?(用助动词过去式did提问,放句首,其它顺序不变,但动词变为原形) Is he writing his paper?(直接提前原肯定句be动词形式,其它顺序不变) 特殊疑问句:(提问"paper") What did he do?(特殊疑问词+did+原句顺序) What is he doing?(特殊疑问词+原肯定句be动词形式+原句顺序