第1个回答 2012-05-26
现在完成时结构:have/has+过去分词
通常和never ever,just,already,yet,before,once,twice,recently,in the past ten years,for,since,how long连用
过去完成时
常和by the end of last year,by 2008,by last term连用本回答被提问者采纳
第2个回答 2012-05-26
already,yet,never,ever,just,so far,至今
for three years ,how long,how many times,three times/twice,since+过去,by+now/today,itis thefist/thirdtime......
in the last few years,in the past few years,in the last ten years,in the past ten years
during the last few years ,during the past few years, during the last ten years ,during the past ten years
over the last few years,over the past few years,over the last ten years ,over the past few years,over the years
第3个回答 2012-05-26
already , ever , never . so far ,up to now .. since,介词短语或从句。 by + 过去时间用过去完成时。