38. Inside an aeroplane, flying at a high altitude, A.the pressure is the same as that outside. B.normal atmospheric pressure is maintained by the use of air pumps. C.the pressure inside is less than the pressure outside. D.normal humidity and partial vacuum are maintained.
Answer: Option B Solution: The air pressure in an aircraft (cabin pressure) is kept higher than the atmospheric pressure at high altitudes to avoid discomfort to passengers due to low outside air pressure. This pressure is called cabin pressurization. Hence the normal atmospheric pressure is maintained by the use of air pumps.
