George, how can you prove the earth is round?—I can’t, sir. ______, I never said it was.

Most students like dinosaurs, but ______ of them know the story of dinosaurs.

He said that he thought of a person _____ one idea and makes it work . [ ]

There is ________ “m” and ________ “u” in the word “much”.

You had better save your time ________.[ ]