Which of the Following Is the Best Example of a Delusion

Which of the following is the best example of a delusion?

A) Zena believes that she is pregnant. After having multiple pregnancy tests and an ultrasound that all show no evidence of pregnancy, she still believes she will be giving birth in just a few months.
B) Elliot wants to be a professional football player when he grows up, despite the fact that he is small for his age and not particularly good at football. Any criticism about his playing just motivates him to practice more.
C) Violet sometimes hears girls in her class whispering about her. When she turns around and asks them why they were whispering, they give her a confused look and said they weren't-she must have been hearing things.
D) Tom thinks he is a very fast runner. He tries out for the track team, and only when five other kids pass him, does he realize that he's not so fast.