NDB台的圆锥效应区的半圆锥角为（）。

Clouds are classified into four families, based on their （ ） ．

The prefix “cirro” is used to denote cumulus and stratus clouds from the （ ） family.

The prefix “alto” is used to name cumulus and stratus clouds from the （ ） family.

The suffix “nimbus”, used in naming clouds, means a （ ） ．

The four families of clouds are （ ） ．

On the high altitude weather chart, the temperature difference between isotherms is （ ） degrees Celsius.

The general characteristics of unstable air are （ ） ．

Clouds, fog, or dew will always form when （ ） ．

What is a characteristic of stable air?

The characteristics of stable air are （ ） ．