The back garden of our house contains a lawn,

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

which is

which it is

it is

where it is

答案及解析：本题考查非限制性定语从句A选项，句意：我家的后花园有一片草坪，夏天坐在上面会令你心旷神怡。which引出非限制性定语从句，在句中作主语，且和sit on 构成动宾关系。类似的句子有：This room is comfortable to live in 这句中live in 和this room构成动宾关系。B，选项，which引出非限制性定语从句，在句中作主语，故排除。C，选项，须由which引导非限制性定语从句，故排除。D，选项，where不能引导非限制性定语从句，故排除。故正确答案为A选项。