Look out!Don't get too colse to the house____roof is under repair.

因为roof前没有the.
the roof of which=of which the roof=whose roof
(the roof the house=the house's roof)

roof 是个名词，前面的词必须能接名词的物主代词，又能修饰the house

whose roof? the house's roof所以选A.whose

C.of which虽能修饰the house但不能连接roof.

of which the roof is under repair
中间加一个the意思表达就对了

of which roof这样搭配是不合语法的