一个DME询问频率对应（）个应答频率。

Viewed from the aircraft, the top of the cloud looks bright, this means that the cloud layer （ ）.

An autopilot is essentially a stabilizing system which （ ） the controls during flight.

“（ ）” is the height above the ground or water of the base of the lowest layer of cloud below 6000m covering more than half the sky.

“Indicated speed” is （ ） .

Radar works on an （ ） principle.

“Radar” means Radio Detection and （ ） .

Flight information centers shall provide flight information service and （ ） service within the regions.

Inertial navigation systems are （ ） devices.

The term knots when referring to speed means （ ） per hour.

A compass needle points to the （ ） .