Answer: B. Petroleum and natural gas are formed from marine microorganisms.
Explanation: Petroleum and natural gas are formed from the remains of marine microorganisms like plankton and algae that lived millions of years ago. As these organisms died, their remains sank to the bottom of the ocean and were buried by sediment. Over time, the organic matter underwent chemical changes due to heat and pressure, transforming into hydrocarbons, which make up petroleum and natural gas. This process is called "diagenesis."