Had the bomb dropped over a populated area of the city , there ____ a great deal of damage．
| A．may be | B．might have been |
| C．may not be | D．mightn’t have been |
The professor could hardly find sufficient grounds________ his arguments in favor of the new theory.
| A．on which to base | B．which to base on | C．to base on | D．to be based on |
Along with the email was my brother’s promise ______ I came first in the competition, he would buy me an MP4.
| A．what | B．that | C．that if | D．whether |
"We can’t go out in this weather," said Bob, ________ out of the window.
| A．looking | B．to look | C．looked | D．having looked |
Scientists are convinced _______the positive effect of laughter ______ physical and mental health.
| A．of ; at | B．by ; in | C．of ; on | D．on ; at |
Many of them turned a deaf ear to his advice, ________ they knew it to be valuable.
| A．as if | B．now that | C．even though | D．so that |