In a set of classic experiments performed in the early 1950s, Urey and Miller subjected an experimental system composed of H2, CH4 (methane), and NH4 (ammonia) to electrical sparks. A few days later, they found in their system.

Amino Acids

Explanation:

The idea of abiogenesis was first proposed by the Oparin and Haldane which was later supported by the experiments of Urey and Miller. This abiogenesis is a scientific theory which states that life arose on Earth via spontaneous natural means due to conditions present at the time. In other words, life came from non-living matter

To prove this, they attempted to create the same environment which was produced billions of years ago that is environment of methane, ammonia, hydrogen gas and electric sparks.  

In this their research, they found simple organic molecule like amino acids a few days after the experiment was performed.

it is b that is the answer.