进场及进近程序设计中对直角坐标系中的Y轴的正负规定是（）。

（ ） clouds are similar to cumulus clouds, except they have more vertical development.

（ ） does not belong to the high clouds.

（ ） is not an example of middle clouds.

（ ） are not included in low clouds.

The average height for 850hpa, 700hpa and 500hpa weather chart is（ ）respectively.

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 （ ） ．