Answer: 10 clouds

High clouds (Family A)
High clouds will form between 10,000 and 25,000 ft (3,000 and 8,000 m) in the polar regions, 16,500 and 40,000 ft (5,000 and 12,000 m) in the temperate regions and 20,000 and 60,000 ft (6,000 and 18,000 m) in the tropical region.[1]

Cirrocumulus (Cc)
Cirrus (Ci)
Cirrostratus (Cs)
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[edit] Middle clouds (Family B)
Middle clouds tend to form at 6,500 ft (2,000 m) but may form at heights up to 13,000 ft (4,000 m), 23,000 ft (7,000 m) or 25,000 ft (8,000 m) depending on the region. Nimbostratus clouds are sometimes included with the middle clouds.[1]

Altostratus (As)
Altocumulus (Ac)
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[edit] Low clouds (Family C)

Stratocumulus clouds, between Cumulus in the foreground and backgroundThese are found up to 6,500 ft (2,000 m)[1] and include the stratus (dense and grey). When stratus clouds contact the ground, they are called fog.

Clouds in Family C include:

Cumulus[2] (Cu)
Cumulus humilis
Cumulus mediocris
Stratocumulus (Sc)
Nimbostratus (Ns)
Stratus (St)

所有跟帖： 

• 字谜：天高云淡白(10 words relate to cloud)来源: 走马读人 -婉蕠- ♀ (152 bytes) () 06/09/2010 postreply 07:19:11

• 以前只知道蓝天白云，原来“云”有不同的种类，学习了，谢谢。 -婉蕠- ♀ (0 bytes) () 06/09/2010 postreply 07:22:47

• Why some clouds look gray? -走马读人- ♂ (0 bytes) () 06/09/2010 postreply 07:53:52

• Why? -婉蕠- ♀ (0 bytes) () 06/09/2010 postreply 17:48:03

• learned those fancy words related to cloud. thanks for sharing -23731241- ♂ (0 bytes) () 06/09/2010 postreply 08:19:17

• Thx! this the least pertinent one in regard to riddle. -走马读人- ♂ (0 bytes) () 06/09/2010 postreply 14:59:19