The dominant gas in the atmosphere that forms clouds is a) oxygen. b) nitrogen. c) water vapor. d) carbon dioxide.

C). water vapor

Condensation is a process by which the gases form of a substance is converted into it's liquid form. It is very important process for water cycle. The water which gets evaporated from the sea or any other aquatic body gets converted into water vapors. The water vapors being low in density reaches upper layers of the atmosphere, where they condense to form clouds. The dominant gas that forms the cloud in the atmosphere is the water vapor.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.