1.Jill has been in Ireland(since)Monday.
2.Jill has been in Ireland(for)three days.
3.My aunt has lived in Australia(for)15 days.
4.Margaret in her office.She has been there (since) 7 o'clock.
5.India has been an indendent country(since)1974.
6.The bus is late.We've been waiting (for)20 minutes.
7.Nobody lives in those houses.They have been empty(for)many yeasrs.
8.Mike has been ill_(for) a long time.He has been in hospita-(since)October.
since+时间点
for+时间段
这是法则,很简单吧