replied to

replied to 是答复了某个人
I have replied to her E-mail.

replied 是已经答复了
I replied her already.

answered to 是回答了某个人
好像不怎么常用,而且answered后面不需要那个to.要举个例子的话...
she has answered my call.

answered for 是为了某个人回答
She answered (his call) for me.