reply to (someone or something)
To offer an answer or response to someone or something. We must reply to this brutal dictatorship's actions with an equal display of force. There's no point replying to someone like him—the only thing he's hoping for is to stir up controversy.
reply to someone or something
to give a response to someone or something. I replied to her already. There is no reason to do it again. I will reply to her letter as soon as I can.