動詞的時態(tài)：
常用的八種時態(tài)：（以do為例）
一般現(xiàn)在、do/does
現(xiàn)在進(jìn)行、am/is /are doing
現(xiàn)在完成、has/have done
一般過去、did
過去進(jìn)行、was/were doing
過去完成、had done
一般將來 shall/will do be going to do be going/coming
過去將來 should/would do was/were going to do was/were going/coming