There is no way of knowing why one man makes an important discovery ______ another man, also intelligent, fails.
| A．since | B．if | C．as | D．while |
Although the causes of cancer ____we do not yet have any practical way to prevent it.
| A．are being uncovered | B．have been uncovering |
| C．are uncovering | D．have uncovered |
These wild flowers are so special that I would do ____I can to save them.
| A．whatever | B．that | C．which | D．whichever |
The computer system____ suddenly while he was searching for information on the Internet.
| A．broke down | B．broke out | C．broke up | D．broke in |
–When can I come for the photos? I need them tomorrow afternoon.
-They ___be ready by 12:00
| A．can | B．should | C．might | D．need |
In our childhood, we were often ___by Grandma to pay attention to our table manners
A.demanded b reminded C. allowed D. hoped