题目内容：

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
why the answer is

优质解答

逗号隔开,非限定性定语从句
关系代词用which
判断先行词是a lawn （一片草坪）
先行词在定语从句中作sit on 的宾语,不能用where
但此时从句还不完整,
所以要补上it is 作为从句的主语和宾语