单项选择题

Before commercial airliners travel faster than sound, problems must 0e solved regarding （）

A．design
B．Construction
C．operation
D．all of the above

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热门试题

单项选择题

Subsonic flight does not produce a sonic boom, because it（）

A．does not disturb existing pressures
B．stays behind its disturbance
C．does not produce great enough changes in pressure
D．stays ahead of its disturbance

单项选择题

Research is under way to （）

A．discover what causes the sonic boom
B．find a means of eliminating the sonic boom
C．produce the sonic boom at low altitudes
D．reduce the sonic boom to tolerable levels