20.當某翼型升力增加時，則阻力 (A)亦增加 (B)不受影響 (C)減少 (D)為零

5. If an aircraft is operating at 40,000 ft. the pressurization ensures that (A)sea level pressure is maintained in the cabin. (B)the cabin pressure is progressively increased until the operational height is reached. (C)the cabin pressure above 10,000 ft. (D)the cabin pressure is equivalent to an altitude of less than 10,000 ft.