I/You/We/They+do（动词）动词形式不变,一般现在时用原形.
I am a student.you are a student too.
We/They go to the school.
He/She/It+does(动词)用单数,一般现在时加‘es'或“s"
he/she is a student.
he/she goes to the school.
如果是过去式,动词就相应的用它的过去式（go went gone）
he/she/i/you/we/they went to school yesterday.
如果是将来时,一般用will do,be going to do.
he/she/i/we/you will go to the school tormorrow.
