题目内容：

After graduated , I joined the army when I was 21.请问为什么不能用graduated,要用graduating呢?
明明是过去式,为什么要用现在时呢? 还有I joined the army,请问可以用I to join the army吗?

优质解答

after是介词‘在……之后’ ,介词后的动词要用ing形式,
不可以用I to join the army,因为to join是动词不定式,而动词不定式不能作谓语.

追问：

谢谢，，还有就是 I started go to primary school in 1988. 为什么这里go to要删掉呢？？ 可以用I started going to primary school in 1988. 或者I started going to school in 1988吗？

追答：

用I started to go to primary school in 1988. 或者I started going to primary school in 1988

追问：

谢谢....那么我想再问一下，如果我改为I was to join the army,,请问这样可以吗？