Scientists are convinced _____the positive effect of laughter _____physical and mental health．
| A．of ;on | B．by; in | C．of ; at | D．on ;at |
By the time he was twelve, Edison _______ to make a living by himself.
| A．would begin | B．has begun | C．had begun | D．began |
Charlie Chaplin______ a great actor from a child, and at last his dream ______.
| A．dreamed to be ; came to true | B．dreamed of being; came true |
| C．dreamed about being ; was come true | D．dreamed of being; realized |
______ time went on , the weather got worse and worse.
| A．While | B．When | C．As | D．With |
The _________ from the top of the tower was very wonderful.
| A．sight | B．view | C．scene | D．scenery |
_______ him this time is difficult.
| A．To refuse | B．Refusing | C．Refuse | D．Refused |