Four friends left one slice of pizza in the kitchen and went into the living room to watch a movie. During the movie, each friend left the room for a few minutes and then returned. At the end of movie, all the friends went back into the kitchen and saw the last piece of the pizza was gone.

　　Do you know who ate it? Only one of these statements is true:

　　Sarah: “Jill ate it.”

　　Jill: “Melody ate it.”

　　Bill: “Who, me? Can’t be.”

　　Melody: “Jill is lying when she says I ate it.”

　　What’s the answer?

　　Bill ate the last slice of pizza.

　　Why?

　　It’s impossible for Sarah’s, Jill’s or Bill’s statement to be the only one that is true. If Sarah’s statement that Jill ate it is true, then Bill’s statement is also true. If Jill’s statement that Melody ate it is true, then Bill’s statement is also true. If Bill’s statement is true, then no one else’s statement can be true. Therefore, Bill’s statement is false, and Melody’s statement is the only true one.