During the First 5-600 Million Years on Earth the Atmosphere

During the first 5-600 million years on Earth the atmosphere was primarily methane,ammonia,and hydrogen,much like other planets in our solar system.How would these conditions favor the formation of biological molecules?

A) Many chemical reactions are favored by high temperature and pressure
B) Many chemical reactions are inhibited by high temperature and pressure
C) Oxygen will break down many organic molecules by reduction
D) Oxygen will break down many organic molecules by oxidation
E) Oxygen is necessary to produce many organic molecules