题目内容：
As the plane circled over the airport, everyone sensed that something was wrong.The plane was moving unsteadily through the air, and 1 the passengers had fastened their seat belts, they were suddenly 2 forward.At that moment, the air-hostess 3 .She looked very pale, but was quite 4 .Speaking quickly but almost in a whisper, she 5 everyone that the pilot had 6 and asked if any of the passengers knew anything about machines or at 7 how to drive a car.After a moment‘s 8 , a man got up and followed the hostesssintosthe pilot's cabin.Moving the pilot 9 , the man took his seat and listened carefully to the 10 instructions that were being sent by radio from the airport 11 .The plane was now dangerously close 12 the ground, but to everyone's 13 , it soon began to climb.The man had to 14 the airport several times insgroupsto become 15 with the controls of the plane. 16 the danger had not yet passed.The terrible 17 came when he had to land.Following 18 , the man guided the plane toward the airfield.It shook violently 19 it touched the ground and then moved rapidly 20 the runway and after a long run it stopped safely.阅读短文回答题。
1.填入正确答案 A．although
B．while
C．therefore
D．then
参考答案：【答案仅供学习，请勿对照自行用药等】
答案解析：