The correct option is A on
To put on clothing or make-up, one places it on one's body in order to wear it. The context refers to wearing a sweater. Hence, the phrasal verb given in option A, put "on" is the correct answer.
To put "in" an amount of time or effort doing something, one spends that time or effort doing it.
To put "down" someone or something is to criticize that.
To put "at" is to calculate or estimate cost, size etc.