Going on a trip into _____ space must be quite _____ exciting experience.
| A．/; the | B．/; an | C．the; the | D．the; an |
Speaking of all the songs he has written, I think this is probably his _______ one.
| A．better-known | B．well-known |
| C．best-known | D．most-known |
I would appreciate it _______ you call back this afternoon for the doctor’s appointment.
| A．that | B．if | C．which | D．whether |
We can never expect _______ bluer sky unless we create _______ less polluted world.
| A．a; a | B．a; the | C．the; a | D．the; the |
We all know that, _______, the situation will get worse.
| A．not if dealt carefully with | B．if not carefully dealt with |
| C．if dealt not carefully with | D．not if carefully dealt with |
The fearless pirates kept _______ on the waters off the coat of Somalia, from the Gulf of Aden to the Kenya border along the Indian Ocean.
| A．knocking on | B．knocking down |
| C．knocking about | D．knocking at |