I was walking along one road of the campus when I saw an old couple coming toward me, they were waving their hands to me, I thought. But I was pretty sure that I didn't know this couple at all although I couldn't see their faces from a distance because of my poor sight. I knew old people always have trouble in memorizing things, maybe they just mistook me for someone else. But anyway, it was polite to give your response when someone say hi to you, so my smile was an answer to them. But later I saw another old women right behind me giving her response to this old couple, so I realize that, it was the old womem, not me, that the old couple were saying hi to. What an embarrassing moment it was!