Riddle: There are two green caps and three red caps. Jack, Lisa and Bill close their eyes, pull out their hats and put them on their heads. It's a game in which three people look at the colors of others' hat and match their hats. Bill and Lisa said they didn't know, but Jack said I knew. What is Jack's hat color?
Answer: It's red because Bill and Lisa wear green hats, and the only red hats are left