在NAIP的机场使用细则中提供的主要障碍物是以（）为圆心，以（）km和（）km为半径分两个表格表示。

A cold front is one where （ ） ．

When judging the wing speed by wind sock, if the wind sock is at aclinic level, then the wind speed can be up to（ ）m/s.

（ ） cannot be an indication to the passage of a frontal system.

When the A/C flies from one airmass into another, an airmass with different（ ）properties may be expected.

The boundary between airmasses is called a （ ） ．

An air mass is a body of air that （ ） ．

A high cloud is composed mostly of （ ） ．

Low clouds usually consist almost entirely of （ ） ．

Fair weather cumulus clouds often indicate （ ） ．

The （ ） is a large body of air with fairly uniform temperature and moisture content.