The following is a question from the university entrance examination held in 2013 using the DNC Japan Test.
My brother ( ) have been very popular when he was a high school student. He still gets lots of New Year's cards from his former classmates.
(1) must, (2) ought to, (3)should, (4) would
The correct answer is (1). I wonder why (3)should can't be a correct answer. If must is an answer, should must be another answer, because both must and should have the meaning of necessity.