Why pleasant smells do not reduce pain in man is a question still _______ by scientists.
| A．answered | B．being answered | C．to be answered | D．that answered |
All animals in nature must learn to to a changing environment in order to survive.
| A．attach | B．adapt | C．respond | D．turn |
Paul was not allowed to work he was fully recovered from the flu.
| A．even if | B．whether | C．because | D．until |
Assistance dogs are trained to help disabled to live more independent life.
| A．/; a | B．a; the | C．the; the | D．the; a |
— Leo, I finally persuaded my mother.
— So we can go to the basketball club tonight.
| A．All the best. | B．Never mind. | C．Well done! | D．Good luck! |
Had he studied harder, he______the final exams.
| A．would pass | B．could pass |
| C．had passed | D．would have passed |