Definition: 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").
Input: Fact1: Lancelet larvae are free-swimming., Fact2: After eggs are fertilized, free-swimming larvae develop., Question: What needs to happen so that lancelet eggs can navigate in the water themselves? (A) fertilization (B) Seconds and minutes (C) key element (D) speed of movements (E) safe operation (F) calibrated (G) visibility (H) protection
Output:
A