On a daily basis, how many passengers with serious in-flight medical problems call for pilots to turn the flight around

A．first-class cabins
B．economy cabins
C．business cabins
D．all cabins

A．2) here means__________.A. an enclosed heavily armored combat vehicle that moves on tracksB. a large receptacle for holding waterC. a corporation or group organized for interdisciplinary research in technological or social problemsD. a prison cell or enclosure used for receiving prisoners