小编给大家带来公共英语考试二级口语辅导练习(18)，希望对大家有所帮助。下面就请大家跟随小编的脚步一起来看看吧。希望各位备考公共英语二级的小伙伴们都能顺利上岸~
　　比较since和for
　　Since 用来说明动作起始时间，for用来说明动作延续时间长度。
　　I have lived here for more than twenty years.
　　I have lived here since I was born……
　　My aunt has worked in a clinic since 1949.
　　Some new oilfields have been opened up since 1976.
　　I have known Xiao Li since she was a little girl.
　　My brother has been in the Youth League for two years.
　　I have not heard from my uncle for a long time.
　　注意：并非有for 作为时间状语的句子都用现在完成时。
　　I worked here for more than twenty years.
　　(我现在已不在这里工作。)
　　I have worked here for many years.
　　(现在我仍在这里工作。)
　　小窍门：当现在完成时 一段时间，这一结构中，我们用下面的公式转化，很容易就能排除非延续动词在完成时中的误使。
　　1)(对) Tom has studied Russian for three years.
　　= Tom began to study Russian three years ago, and is still studying it now.
　　2)(错) Harry has got married for six years.
　　= Harry began to get married six years ago, and is still getting married now.
　　显然，第二句不对，它应改为 Harry got married six years ago.或 Harry has been married for six years.