What Source of Energy Was Used to Trigger the Manufacture

Multiple Choice

What source of energy was used to trigger the manufacture of complex organic compounds in laboratory simulations of conditions in primordial planetary atmospheres?

A) thermal heating, to simulate volcanic heating
B) electric discharges, to simulate lightning
C) heat from chemical reactions in early reactive planetary atmospheres
D) UV and visible radiation, to simulate the intensity of sunlight at earlier times in planetary life