Duringflight,middleearbarotraumasoccursmainlywhen（）
A. flyingbelow1000m.
B. flyingabove6000m.
C. flyingbelow4000m.
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Howtopreventandovercomemiddleearbarotraumas?（）
A. Putonheadphones.
B. TakeinasmallbagofCO2、
C. Movethesoftpalateormakeswallowingmotion.
Whichfactormaybeassociatedwithgrayout?（）
A. positive-G
B. negative-G
C. 0-G
Whichfactorsareassociatedwiththeincidenceofradiation?（）
A. Temperatureandhumidityinanairplane.
B. Flighttime,flightheightandthespaceexposedtothesun.
C. Airspeedandatmosphereconcentration.
Thehumanbodyfeelscomfortablewhenthehumidityisabout（）
A. 40%-60%
B. 50%-60%
C. 30%-60%
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