Final answer:
Petroleum and chlorinated organics can be completely degraded to carbon dioxide by microorganisms.
Step-by-step explanation:
The correct answer is D) petroleum and chlorinated organics. Petroleum, which consists of hydrocarbons, can be completely degraded to carbon dioxide by microorganisms. Chlorinated organics, such as chlorinated solvents, can also be degraded by certain microorganisms through a process called biodegradation, which converts them into simpler compounds including carbon dioxide.