b. merry

You should note that gay in fact means all of the above. Over time a series of semantic changes has occured in the word. It started out in the 13th century as `merry`; in the 14th century it acquired the meaning of `colorful`; then it took on the meaning of `licentious` (i.e., lacking sexual restraint) in the 17th century; and, finally, it came to mean `homosexual`, the predominant contemporary meaning.