Good Riddles

Question: How do you spell mousetrap with three letters?

Question: What goes up white and comes down yellow?

Question: You need a room for your group. Each person needs 5 square feet of space. You have 25 people in your group, what is the smallest room you can use?

Question: Something you know nobody knows, and everyone knows something you don't. We all know something, nobody knows everything, and you know something someone doesn't know. What else could nobody know?

Question: Have a question , regardless you ask any people , that people only give you answer is " no " , what is this question ??