Moving the pilot aside, the man took his seat and listened carefully to the urgent instructions that were being sent by radio from the airport below. The plane was now dangerously close【B6】the ground, but to everyone's relief, it soon began to climb. The man had to【B7】the airport several times in order to become【B8】with the controls. Therefore the danger had not yet passed. The terrible【B9】came when he had to land. Following information, the man guided the plane toward the airfield. It shook violently【B10】it touched the ground and then moved rapidly along the runway and after a long run it stopped safely.
【B1】

A. although
B. while
C. therefore
D. then