It’s not necessary to explain the truth ____ there is spring wind, there is green grass. [ ]

How difficult math is! I really want to drop it ! —_________you come on，you will do it better．

Why not ask Tony to go to the cinema together with us —He _____Shanghai on business , and ____back in two weeks .

___________ does the girl look —She is very small and thin.

Only six _______ of the students here _______ from China and they are very hard working.