I had a hard time learning math last year. 

--What’s wrong with you? ---I have a _______.The doctor asked me not to eat anything today because I ate too much yesterday.

Michael Jordan is a man who never gives up in his life. And that's _________ he succeeds．

Though it rained heavily, it didn’t make much _______ to the game.

We stayed there and watched the opera ______ an hour.