[单项选择]Air pollution causes airplane accidents because ______.


A. pilots become ill
B. visibility is reduced
C. engines fail.
D. the air is too hot

[单项选择]Air pollution causes airplane accidents because ______.


A. pilots become iii
B. visibility is reduced
C. engines fail.
D. the air is too hot

[单项选择]I'm moving to the countryside because the air there is much fresher than （　） in the city.
A. ones
B. one
C. that
D. those

[单项选择]Cold air causes the arteries around the heart to constrict.


A. become rigid
B. contract
C. close
D. die

[单项选择]Because of the reduction of air pollution, this city now is a good place（）.
A. where to live
B. which to live
C. to live in
D. to be lived

[单项选择]The computer is important to the air line because ______.


A. it sells tickets
B. it writes out tickets
C. it gives the information needed
D. it knows when a plane takes off.

[单项选择]The dolphin leapt into the air because ______.
A. Sagan had turned his hack
B. it was part of the game they were playing
C. he wanted Sagan to scratch him again
D. Sagan wanted him to do this

[单项选择]Air France has made such a decision because ______.


A. it has received terror alerts
B. there is no evidence of any terrorist attack
C. it is facing pressure from the U. S.
D. it has invited cooperation from the U. S.

[单项选择]What causes tide


A. The pull of the sun and the moon.
B. The heat of the sun.
C. The shape of the moon.
D. The light of the moon.

[单项选择]The airplane was reported to have crashed.
A. 飞机被报告即将坠毁。
B. 飞机被报道即将坠毁。
C. 据报道，飞机即将坠毁。
D. 据报道，飞机已坠毁。

[填空题]Anyone who sees a special type of airplane with its turning wings knows it is a helicopter’s. One of the helicopter’s most important{{U}} (36) {{/U}}is its ability to fly as slowly as it likes. It can do more than that. It can move{{U}} (37) {{/U}}, {{U}} (38) {{/U}}and sideways. It can also stay in the air without{{U}} (39) {{/U}}at all. Above all it can move up and down in a completely {{U}} (40) {{/U}}line: the ability to take off and land is the most{{U}} (41) {{/U}}For in this way it can deliver goods and{{U}} (42) {{/U}}to places which could not possibly be reached by{{U}} (43) {{/U}}planes, It can land in a very small field. It can land on a road or on a small ship.{{U}} (44) {{/U}}They are used for loading ships and for building things of all kinds. The big oil companies use them for sending supplies to men scathing for oil under the sea. {{U}} (45) {{/U}}Every day somewhere in the world lives are saved by helicopters. {{U}} (46) {{/U}}Ordinary airplanes canno