Question

The back garden of our house contains a lawn, _____ very pleasant to sit on in summer.

A. which is B. which it is C. it is D. where it is

我就在纠结A和B。我觉得A是对的，可答案是B。网上到处A、B的答案都有，众说纷纭。到底为什么？

Answer 1

只能是选B，只要把句子还原，The back garden of our house contains a lawn, It’s very pleasant to sit on which in summer.
而要说服你不选A，也不难。
如果要选A，这个逗号是要去掉的，那么句子就变成The back garden of our house contains a lawn which is very pleasant to sit on in summer.，这样lawn作先行词在后面的从句中充当主语，这是完全可以的。
所以说这题的关键就在于这个小小逗号，它的存在决定了两种不同的表达。

Answer 2

• 该选B,which指代a lawn ,which在从句中做to sit on 的介词宾语。后面从句还原为It’s very pleasant to sit on which in summer. to sit on which又做从句的逻辑主语。
  

Answer 3

B
这里是个非限制性定语从句，原本应该是这样的：It is very pleasant to sit on the back garden in summer.

Answer 4

非限定性定语从句 句中it带指sit on the back garden这一件事 原句可为: It is very pleasant to sit on the back garden of our house in summer.