If we _______ now to protect the environment, we'll live to regret it.
| A．hadn't acted | B．haven't acted |
| C．don't act | D．won't act |
I was caught in a traffic jam for over an hour, otherwise I ________ you waiting for such a long time.
| A．will not keep | B．have not kept | C．had not kept | D．would not have kept |
– Amazing! You _____ have won the first prize in the national English speech contest!
– I’m lucky that all my efforts have finally paid off.
| A．must | B．may | C．can | D．should |
A qualified doctor has to constantly update his knowledge in order to maintain his professional _____.
| A．conscience | B．competence | C．conservation | D．convenience |
We all consider _____ significant that we should cancel the order immediately.
| A．how | B．which | C．this | D．it |
_____, everyone present was amused by his adventure story in Africa.
| A．Absurd as might it sound | B．As it might sound absurd |
| C．As absurd it might sound | D．Absurd as it might sound |