机载测距机和地面测距信标台配合工作，可连续地向（）提供飞机到测距台的实时距离信息。

The radio call to alert ground personnel when an A/C is having difficulty, but is in no immediate danger, is （ ）.

When ground-air communication failure occurs, controller should （ ）.

If air-ground communication failure occurs, the pilot should （ ）.

To transfer communication with an A/C to another unit, the controller should pass instructions giving （ ）.

Readback is necessary in RTF because （ ）.

A controller should pass ATC clearance to a pilot at the time （ ）.

In which case a controller is not supposed to say NEGATIVE（ ）.

After receiving takeoff clearance, pilot must takeoff within （ ） minutes or he will ask for a new clearance/.

The abbreviated call sign of N357826 is （ ）.

In RTF communication, the A/C call sign 9099Y is spoken as （ ）.