The truth, Sir, is that the old man____ across the street when my car hit him.
| A．was to walk | B．had been walking | C．walked | D．was walking |
Playing on a frozen sports field sounds like a lot of fun. Isn't it rather risky，__________？
| A．though | B．also |
| C．either | D．too |
Hot __________ the night air was, we slept deeply because we were so tired after the long journey.
| A．although | B．as |
| C．while | D．however |
__________ the police thought he was the most likely one, since they had no exact proof about it, they could not arrest him.
| A．Although | B．As long as |
| C．If only | D．As soon as |
__________ H7N9 is a deadly virus, it is still safe to eat thoroughly-cooked chicken.
| A．Until | B．While |
| C．If | D．Since |
__________ you may have, you should gather your courage to face the challenge.
| A．However serious a problem |
| B．Whatever serious a problem |
| C．However a serious problem |
| D．No matter how a serious problem |