答：关系代词whose 可以引导定语从句,在从句中作定语,加上一个名词（这里是roof)后一起在从句中作主语或宾语.whose不仅可以指代人,表示“他/她/他们的”,也可以指事物,表示“它/它们的”,用一个汉字“其”可综合所有的“Ta （们）的”
房顶,英语中可以用its roof,也可以用the roof of the house,改成定语从句时,有两种方式：
whose roof,和the roof of which,后者常写成of which the roof ...
有人说of which =whose 是不确切的,容易犯错误的,因为whose后就不能再用the,面of which 前面（或后置的这个）名词前应有一个the表示特指才行.
The house (whose ) roof was damaged has now been repaired.
=The house of which the roof was damaged has now been repaired.
译：原先（其）顶受损的那间房子现在已经修好了.
注：非限制性定语从句,还可以说成,the roof of which ...
如：My house,the roof of which was damaged,has now been repaired.
也可能用上面的两种说法：My house,whose roof...,./ My house,of which the roof...,.
但限制性的,一般只用上面的两种,不太用：The house the roof of which was .,语感不是很好.