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Read Bridge to Terabithia, by Katherine Paterson
What does Jess threaten to do if May Belle follows him again or squeals to Momma about where he and Leslie goes?
Answer: Jess threatens to tell Billy Jean Edwards May Belle still wets the bed sometimes.
Step-by-step explanation:
Jess wants to keep Terabithia, the secret fantasyland he and Leslie created, a secret between him and Leslie alone. May Belle, his six-year-old sister, has followed them, and discover their doings, so Jess threatens her with something that could be very upsetting for a girl that age, telling a boy about her still wetting the bed.