The correct option is
A Supported
THREW COLD WATER ON means to discourage or try to prevent a plan or something unenthusiastic. And the antonym of the given group of words is to encourage or to support which is similar to the meaning of the word given in option A. Therefore option A is the correct option.
Whereas option B means failure, option C means alter, change or revise, Option D means to improve or remodel.