The first try

Rule 3: If the number of children is not specified, the woman will simply get pregnant with one child the next time she has sex.

After considering carefully, John picked a candidate for his test: Rachel, a girl in his Literature class. She was a shrinking violet and thought herself a bit ugly due to her freckled face. John knew for sure that she didn't have any boyfriend and was still a virgin.

He wrote her name into the note and wait.