用一般過去時(shí)代替完成時(shí)

1) 構(gòu)成will / be going to do sth.

2) 概念　 a. 狀態(tài)完成：表示某事繼續(xù)到將來某一時(shí)為止一直有的狀態(tài)。 b. 動(dòng)作完成：表示將來某一時(shí)或另一個(gè)將來的動(dòng)作之前，已經(jīng)完成的動(dòng)作或一獲得的經(jīng)驗(yàn)。 They will have been married for 20 years by then. You will have reached Shanghai by this time tomorrow.