The chair looks rather hard,but in fact,it is very comfortab

The chair looks rather hard,but in fact,it is very comfortable to_______.
A.sit on B.be sat on
答案选的是A 估计是省略了for sb to do 的结构 但是不定式的逻辑主语是其动作的承受者时不是应该用被动语态的吗?
--Shall we go skating or stay at home?
--Which _____ do yourself?
A.do you rather B.would rather C.will you rather D.should you rather
选什么 为什么