行为动词的一般现在时和一般过去时,变疑问句和否定句时,谓语动词要还原.如果就主语提问时,谓语动词不变.例如
1.He studies English hard.(变一般疑问句和否定句)
Does he study English hard?
He doesn't study English hard.
He studies English hard.（就程度状语问句）
How does he study English?
He studies English hard.（就主语提问时谓语动词不变）
Who studies English hard?
2.He did his homework at 4:00 in the afternoon.( (变一般疑问句和否定句)
Did he do his homework at 4:00 in the afternoon?
did（助动词,无词意）,do (谓语动词,做).
He did not do his homework at 4:00 in the afternoon.
第一个did是助动词无词意,帮助do构成否定句.第二个do是谓语动词必须还原.（时态,人称,数要求在助动词上体现.）
He did his homework at 4:00 in the afternoon.（就时间状语问句）
When did he do his homework?（理由同上）
He did his homework at 4:00 in the afternoon.（就主语提问时谓语动词不变）
Who did (谓语动词,做)his homework at 4:00 in the afternoon.