Problem: Nelson got good grades in graduate school, unlike Nick because

My choice: Nick was lazy during the tests.

Problem: Patricia had a lot more friends than Monica, because

My choice: Monica was not very outgoing or friendly.

Problem: Christine caught the cold at school, but Felicia stayed healthy, because

My choice: Felicia had a strong immune system.

Problem: The stomach of Neil was rumbling, but Samuel seemed fine, due to

My choice:
Neil being hungry.