No one has yet succeeded in solving the _____ of how life first began.
| A．biology | B．gravity | C．puzzle | D．theory |
—I’ll be away on a business trip for a week. Would you mind looking after my dog?
—Not at all..
| A．I’ve no time | B．I’d rather not | C．I’d like it | D．I’d be happy to |
—Is that the country clinic you often refer to?
—Right，just the one you know my father used to work for 10 years
| A．that | B．which | C．where | D．as |
—John, how did your English exam go?
—I thought I _____, but in fact I came in the top 10% in the class.
| A．should have failed | B．might have failed |
| C．couldn’t have failed | D．mustn’t have failed |
For professional athletes, ________ to the Olympics means that they have a chance to enter the history books.
| A．access | B．attachment | C．appeal | D．approach |
Try to spend your time just on the things you find _________.
| A．worth doing them | B．worth being done |
| C．them worth doing | D．worth doing |