在說(shuō)或?qū)懸痪湓挄r(shí)，通常要選擇一個(gè)中心時(shí)態(tài)，這個(gè)中心時(shí)態(tài)影響其它時(shí)態(tài) ，即時(shí)態(tài)要前后一致。

　　以現(xiàn)在為中心：若開始敘述或描述著眼于現(xiàn)在，則常以現(xiàn)在為起點(diǎn)，從而會(huì)出現(xiàn)一般現(xiàn)在時(shí)、現(xiàn)在進(jìn)行時(shí)、現(xiàn)在完成時(shí)或一般將來(lái)時(shí)連用的情況。

　　Our postman usually delivers our arrival at 7 every morning. It (be) nearly lunchtime and the mail still (not arrive). I (suppose) the mail (come) soon. Perhaps he (be) ill. (is, hasnt arrived, suppose, will come, is

　　以過去為中心：若著眼于過去，則常以過去某時(shí)為基點(diǎn)，從而出現(xiàn)一般過去時(shí)、過去進(jìn)行時(shí)、過去將來(lái)時(shí)和過去完成時(shí)連用的情況。

　　We lived in the street. They (build) houses all around us then. We (be) there for 10 years and (imagine) we (stay) there for the rest of our lives. (were building, had been, imagined, would stay)