My mother is __________ in her family

My mother is __________ in her family.
A.the shorter
B.the shorter than
C.the shortest

I like sushi, but Chinese food is __________.
A.better
B.the better
C.more better
My drink is __________ of all the drinks.
A.colder than
B.the coldest
C.the most cold
My sister is __________ student in her class.
A.smarter than
B.the smarter
C.the smartest