He is the only one of the students who _________ a winner of scholarship for 3 years.
| A．is | B．are | C．have been | D．has been |
Although he knew little about the large amount of work done in the field , he succeeded other more well-informed experimenters failed.
| A．as | B．unless | C．what | D．where |
John waited at the bus-stop for nearly half an hour the bus finally arrived .
| A．when | B．as | C．before | D．while |
Not that I’m unwilling to lend you a hand ,I’m too busy for the moment .
| A．because | B．but that | C．but | D．however |
Jack had traveled six miles across the Channel _____his engine failed and was forced to land on the sea .
| A．when | B．until | C．after | D．since |
—When did he leave the classroom?
—He leftyou turned back to write on the blackboard.
| A．the minute | B．the time | C．until | D．before |