Question: The girl went down the hill on her bike. What is the effect?

Answer: Her bike sped up.

Question: The guests of the party hid behind the couch. What is the cause?

Answer: It was a surprise party.

Question: The woman's makeup smeared. What is the cause?

Answer: She wiped her eyes.

Question: My stomach hurt. What is the cause?

Answer:
I ate birthday cake.