What kind of monologue should I prepare to audition with for a whodunnit?

My high school is about two weeks away from auditions for Agatha Christie's "And then there were None". I've only auditioned for Romeo and Juliet before, so I'm not sure what kind of a monologue to memorize for this one. The only restriction is that it has to be between a minute and a half and two minutes. They might also have you read cold from the script with two other actors. The play is about ten contrasting people who get sent to an island and eventually all of them die. The director has already told me that he is planning on having the ten actors along with five understudies. He also said that one of the characters, a spoiled preppy-looking man, will be casted as a female. What kind of monologue would you recommend for this kind of a play?