求解2题英语My sister didn't go to the party last night because sh

求解2题英语
My sister didn't go to the party last night because she_____the baby for her friend until 9:30
A must have looked after
b would have to look after
c had to look after
d should hae looked after
He has written several books,but his last works_______well known among his friends.
A have
b have been
c is
d are