Q: You are presented with the quiz "What has to happen for roundworms to reproduce?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "roundworms reproduce sexually" and "fertilisation is a key feature of sexual reproduction". So, what's the best answer to the question?

pick from the following. [i] Fertilization. [ii] rapid expansion. [iii] Plants growth. [iv] an organism's body. [v] permineralization. [vi] bioaerosols. [vii] temperature changes. [viii] competition.
A:
[i]