Is there anything ______?
| A．you are not sure |
| B．about which you not quite sure |
| C．that you don’t understand |
| D．which you don’t understand |
He was so deep in thought，thinking of the problem ________ he knocked into the tree without noticing it.
| A．when |
| B．while |
| C．because |
| D．that |
________you’ve experienced it，you can’t understand how I felt.
| A．Once |
| B．Because |
| C．Unless |
| D．While |
________ you may have，you should gather your courage to face the challenge.
| A．However a serious problem |
| B．What a serious problem |
| C．However serious a problem |
| D．What serious a problem |
Paul was not allowed to work he was fully recovered from the flu.
| A．even if |
| B．whether |
| C．because |
| D．until |
She cared more about her students than her own health. That’s why two years passed _____ she was treated for breast cancer.
| A．since |
| B．before |
| C．after |
| D．until |