二十一、For the past + 时间，S + 现在完成式...(过去...年来，...一直...)
例句：For the past two years, I have been busy preparing for the examination.
过去两年来，我一直忙着准备考试。
二十二、Since + S + 过去式，S + 现在完成式。
例句：Since he went to senior high school, he has worked very hard.
自从他上高中，他一直很用功。
二十三、It pays to + V ~~~ (...是值得的。)
帮助别人是值得的。
二十四、be based on (以...为基础)
例句：The progress of thee society is based on harmony.
社会的进步是以和谐为基础的。
