1. 어느 분이(or 께서) 알려주셨어요? ☞ Who let you know that? ("알려주시다" is the honorific form of "알려주다") 2.I'd say "one's name님께서 알려주셨어요". We seldom use the term "당신" as to "you", we usually address one's name instead. e.g. N0o0Na226님께서 알려주셨어요. N0o0Na226가 알려줬어요(not polite) \^o^/