現(xiàn)在完成時have done 的時間標志是
in the past few/three years
since + 時間點/ sb dis
副詞標志是
already,yet,never,ever
現(xiàn)在完成時可以單獨使用
i have finished homework.
但過去完成時不可以單獨使用
用在“It is the first/second...time+that”從句中
過去完成時 had done
時間標志
by last year/by the time of
過去完成時一般和過去時一起出現(xiàn)
sb had done sth before sb did
sb did sth after sb had done
用于hardly when,no sooner than的句式中
we had hardly came home when it rained.
用在“It was the first/second...time+that”句型中