Scientists are convinced___the positive effect of laughter___physical and mental health.（）
| A． | of;at | B． | by;in |
| C． | of;on | D． | on;at |
Tom _________ in the library every night over the last three months.
| A．works | B．worked | C．has been working | D．had been working |
Although cats can not see in complete darkness, their eyes are much more _______to light than human eyes.
| A．brilliant | B．attractive |
| C．available | D．sensitive |
There’re more than 100 elements found in nature, ______ are metals.
| A．most of which | B．most of them | C．most of that | D．most which |
— Tony，you look upset. What’s the matter？
— I had my proposal _______ again.
| A．turned over | B．turned on | C．turned off | D．turned down |
______ Father offers to us children is honesty and kindness.
| A．Which | B．What | C．That | D．Whom |