--- Could you tell me why I am constantly yawning this afternoon?
---Yawning ______ an indication that your body lacks oxygen and needs a rest.
| A．acts as | B．serves as | C．functions as | D．plays as |
The first person was Tony Garcia from Colombia, closely followed by Julia Smith from Britain.
| A．to arrive | B．arriving | C．arrived | D．arrives |
People have always been curious how living things on the earth exactly began.
| A．in | B．at | C．of | D．about |
Zhang Ning managed to her injury to win the Olympic gold medal.
| A．prefer | B．overcome | C．injure | D．shock |
Up to now nobody able to do this better than Charlie Chaplin.
| A．is | B．has been | C．was | D．will be |
It was John we won the game.
| A．because; who | B．because of; whom | C．as; that | D．thanks to; that |