You are presented with the quiz "Plant reproduction often requires something that causes what?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "plant reproduction often requires pollen" and "hay fever or pollen allergy is the most prevalent allergy". So, what's the best answer to the question?

pick from the following.
(a). mutations.
(b). bloom time.
(c). An earthquake.
(d). Steam.
(e). seeds.
(f). The common cold.
(g). gene flow.
(h). Allergies.
Answer:
(h).