如题所述
先要明白一个前提，动词的现在时才讲究第三人称单数的，呵呵，也就是但凡看到谓语动词用得是原形或者三单都一般都出现在以下几种时态。
he wants to go home now.一般现在时
he is doing his homework.现在进行时，他正在做作业。
he has done his homework.现在完成时，他已经做作业了。
he has been doing his homework.现在完成进行时，他已经一直在做作业了。
在过去时态，过去完成时，将来时等时态中不涉及三单问题的。
明白了吗？
he wants to go home now.一般现在时
he is doing his homework.现在进行时，他正在做作业。
he has done his homework.现在完成时，他已经做作业了。
he has been doing his homework.现在完成进行时，他已经一直在做作业了。
在过去时态，过去完成时，将来时等时态中不涉及三单问题的。
明白了吗？
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第1个回答 2012-05-17
用例子能说明问题。
He goes to school by bus everyday.
He went to school yesterday. (你总不能说，He goes to school yesterday.)
He will go to school tomorrow.
He goes to school by bus everyday.
He went to school yesterday. (你总不能说，He goes to school yesterday.)
He will go to school tomorrow.
第2个回答 2012-05-17
一定以时态为准，没得商量的，在任何情况下都是，希望能采纳
第3个回答 2012-05-17
把事态中的be动词变成is 就可以了。
第4个回答 2012-05-17
动态优先
