現在完成時可以用來表示發生在過去某一時刻的,持續到現在的情況,常與for,since連用.
Mary has been ill for three days.
I have lived here since 1998.
現在完成時往往同表示不確定的過去時間狀語連用,如already, yet, just, before, recently,still, lately等:
He has already obtained a scholarship.
I haven't seen much of him recently (lately).
We have seen that film before.
Have they found the missing child yet