11.10 比較過(guò)去時(shí)與現(xiàn)在完成時(shí)

　　 她已從巴黎回來(lái)了。
　 She returned yesterday.
　　 她是昨天回來(lái)了。
　 He has been in the League for three years.
　　(在團(tuán)內(nèi)的狀態(tài)可延續(xù))
　 He has been a League member for three years.
　　(是團(tuán)員的狀態(tài)可持續(xù))
　 He joined the League three years ago.　
　　( 三年前入團(tuán)，joined為短暫行為。)
　 I have finished my homework now.　
　
　 ---Will somebody go and get Dr. White?
　 ---He's already been sent for.　
　 句子中如有過(guò)去時(shí)的時(shí)間副詞（如 yesterday, last, week, in 1960）時(shí)，不能使用現(xiàn)在完成時(shí)，要用過(guò)去時(shí)。
　 （錯(cuò)）Tom has written a letter to his parents last night.
　 （對(duì)）Tom wrote a letter to his parents last night.