Answer: B. Formed when lightning struck water.  


In 1950, two biochemists named as Harold Urey and Stanley Miller performed an experiment to demonstrate the conditions mimicking the early earth atmosphere.

These scientists designed an apparatus which consist of mixture of gases ammonia, methane, water vapor, and carbon dioxide mimicking that of early earth atmosphere and also added water inside the apparatus. The electric current was passed by the electrodes, which helped in mimicking the effect of natural lightening inside the apparatus. They left the experiment run for a week and then analyzed the contents of the apparatus. They found that different kinds of amino acids which are the responsible for the synthesis of proteins developed after this process. The proteins are the building blocks of life.

It was concluded that the life originated from simple substances on early earth.