Scientists have decided to declare ____ war on AIDS in order to make ____ breakthrough in treating it.
| A．a, a | B．/, a | C．a, the | D．/ , the |
—Thank you very much for helping me out of trouble, Bob.
—________.
| A．With pleasure | B．My pleasure | C．That's right | D．I hope so |
Cheer up! It won’t be ______ we can meet again.
| A．before long | B．long before |
| C．after long | D．long since |
______ the ancient Egyptians built the pyramids puzzled people for centuries.
| A．Whether | B．What | C．How | D．Where |
The boy as well as the two dogs _____ when the earthquake rocked the city.
| A．were sleeping | B．is sleeping |
| C．was sleeping | D．are asleep |
—Sorry, the tickets have already been sold out.
—Really? Maybe I _______ a little earlier.
| A．should come | B．should have come |
| C．could have come | D．must have come |