例：write為原形 一般現(xiàn)在時：He writes his paper.
肯定句：He wrote his paper.（把動詞原形變?yōu)檫^去式即可）
He is writing his paper.[把動詞原形變?yōu)閎e(注意人稱am,is,are）+v.-ing]
改為：
否定句：He didn't write his paper.(可以理解為把過去式“轉(zhuǎn)移”到助動詞上變?yōu)閐idn't,動詞則變回原形）
He isn't writing his paper.(可以理解為直接be動詞后加not,即為否定形式）
一般疑問句：
Did he write his paper?(用助動詞過去式did提問,放句首,其它順序不變,但動詞變?yōu)樵危?br/>Is he writing his paper?(直接提前原肯定句be動詞形式,其它順序不變）
特殊疑問句：（提問"paper")
What did he do?（特殊疑問詞+did+原句順序）
What is he doing?（特殊疑問詞+原肯定句be動詞形式+原句順序