Received a PM asking me to reply (a long time ago). I have been traveling and haven't been on BTG for several weeks. Sorry I haven't replied yet.
As shalinder said, "to" is the correct usage in the above example. This is just an idiom, so there's no real explanation, beyond "a response TO a request" is the correct idiom and "a response FOR a request" is not. Idioms are annoying - just something we need to memorize.
Please note: I do not use the Private Messaging system! I will not see any PMs that you send to me!!
Stacey Koprince
GMAT Instructor
Director of Online Community
Manhattan GMAT
Contributor to Beat The GMAT!
Learn more about me