What is the classification of clouds based on?

High clouds (CH)

Base usually 20,000 ft or above, over British Isles

Medium clouds (CM)

Base usually between 6,500 and 20,000 ft over British Isles.

Low clouds (CL)

Base usually below 6,500 ft over British Isles.

"a connection, a bond or common feeling between two people", or as a chemical process it stimulates love or sexual attraction

the answer is b & c i believe : )