有这样一道考题:It’s reported that the city needs more landA.on which to build housesC.which to build housesB.on which building housesD.which to build houses on 此题答案为A,许多同学不明白此句是什么结构。简单地说,这是一个紧缩了的定语从句,这类结构可归纳为“介词+关系代词+不定式”形式。在正式文体中,当引导定语从句的关系代词用作介词的宾语时,有时可用“介词+关系代词+不定式”这样的结构来简化定语从句。如: