机场障碍物A型图，在某跑道中线延长线上距起飞离场末端400m的地方有一条河，当轮船通过时其桅杆高为5m，则该轮船:（）。

When an airmass is warmed from below, its stability is （ ） ．

The tendency of an airmass to resist vertical motion is called （ ） ．

If an airmass forms over water, its classification is （ ） ．

（ ） results when the two airmasses are approximately equal in pressure.

（ ） is a weather phenomenon always associated with a thunderstorm.

Squall lines most often develop （ ） ．

In TAF, BR stands for （ ） .

（ ） are least likely to contribute to structural icing on an aircraft.

（ ） clouds have the greatest turbulence.

（ ） is the weather phenomenon that signals the beginning of a thunderstorm.