Statement $P$: $A$ major portion of organic matter in water is consumed by chemical processes.
Statement $Q$: Microorganisms,including bacteria,consume organic matter present in water.

• A
  Statement $P$ is true,but Statement $Q$ is false.
• B
  Statement $P$ is false,but Statement $Q$ is true.
• C
  Both Statement $P$ and Statement $Q$ are true,and Statement $Q$ is the correct explanation of Statement $P$.
• D
  Both Statement $P$ and Statement $Q$ are true,but Statement $Q$ is not the correct explanation of Statement $P$.