Until recently historians assumed that calendars ________ with the advent of agriculture.
| A．came to existence | B．came to existing |
| C．came to exist | D．were existential |
Many people in the west make ________ a rule to buy Christmas presents for their relatives and friends.
| A．this | B．it | C．that | D．them |
They were all very tired, but ________ of them would stop to take a rest.
| A．any | B．some | C．none | D．neither |
Come and see me whenever ________.
| A．you are convenient | B．you will be convenient |
| C．it is convenient to you | D．it will be convenient to you |
--The plane is due to take off at 7∶50 from the airport.
--________ we fail to arrive there in time?
| A．What if | B．As if | C．Even if | D．Only if |
--They ________ out the problem, but failed.
--What a shame ! I never thought it was going to happen like that.
| A．managed to work | B．managed working |
| C．sought working | D．sought to work |