$P$: In vertebrates,about $80\%$ of the total phosphorus is associated with teeth and bones.
$Q$: Phosphorus is a structural component of vitamins like biotin and thiamine.

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