It's comfortable_______ on the sofa.A.sat B.sitting C.to sit

It's comfortable_______ on the sofa.A.sat B.sitting C.to sit
It's comfortable_______ on the sofa.A.sat B.sitting C.to sit

It's comfortable_______ on the sofa.A.sat B.sitting C.to sit
B、
Sitting on the sofa is comfortable~

sitting

c 类似的还有 ：It's easy /difficult to learn.等一类的。符合it's+形容词 +to do 结构

选C，it is comfortable to do sth

选B sitting
it 作为形式主语代替后面的sitting on the sofa
原句可以改为：Sitting on the sofa is comfortable....
采纳我的吧~楼主~