介词的使用看你的基本功了,介词一般根据意思来判断,如in表示“在...里”,但有的介词词义较多,还有固定搭配,需点滴积累.

　　定语从句中“介词+which”=where/when,在定语从句里作地点或时间状语,介词根据具体情况而变,其实是介词提前.例如：

　　Doyoustillrememberthetime?Weworkedonthefarmatthattime合成定语从句

　　Doyoustiillrememberthetimewhen(=atwhich)weworkedonthefarm?.

　　when/atwhich代替了atthattime

　　YesterdayIvisitedthepark.Weplantedmanytreesandflowersintheparklastyear

　　.合成定语从句为

　　YesterdayIvisitedtheparkwhere/inwhichweplantedmanytreesandflowerslastyear.

　　where/inwhich代替了inthepark

　　相信你能理解和赞同!祝你不断进步!