首先，前提条件是一般现在时，其次是没有情态动词时，另外还有此动词是做谓语时。比如：1、He wanted to play football last Sunday. But his father did not agree.2.She can play the piano. 3. Lucy needs to go to school by bus.
一般现在时，其次是没有情态动词时，另外还有此动词是做谓语时。
