_______ 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 |
--- What is your strongest memory of the bombing attack?
--- If I ______ rightly, we were about to approach the finish line when a big bang struck my ears.
| A．will remember | B．had remembered | C．remember | D．remembered |
More and more people have come to realize that if we had taken effective measures much earlier, the air quality ______ so seriously now.
| A．is not polluted | B．would not be polluted |
| C．had not been polluted | D．would not have been polluted |
As for friendship, remember that no time is ever wasted _______ makes two people better friends.
| A．what | B．that | C．when | D．as |
The golden rule is not to waste time waiting for opportunity. Begin, ______ opportunity will find you.
| A．and | B．when | C．so | D．because |
---Mom, where is my lunch pack?
---Just where it _______.
| A．has been | B．had been | C．was | D．be |