In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").
Q: Fact1: a mutation in the sex cells of a parent can cause a new trait to appear in the parent 's offspring, Fact2: Alleles arise by mutation., Question: What can cause new alleles to appear? (A) skin cells (B) coded genes (C) sperm and egg fuse (D) hair cells (E) the parent's sex cells (F) lung cells (G) male gametes (H) reproduction
A:
E