To have cold feet means to feel too frightened to do something that you had planned to do. Hence, option C , to lose confidence would be the correct meaning of the given phrase.
Option A is incorrect because ‘to feel very cold’ shouldn’t be felt as cold in the feet alone hence it is incorrect.
Option B is incorrect because ‘to pay much attention to’ means to focus a lot on a particular thing, which is not even close to having cold feet as an idiom.
Option D is incorrect because ‘to pour water on something’ means to spoil whatever has been done, which is incorrect because it is not related to having cold feet.