Consider the following:
Assertion $(A)$: Aspirin is useful in the prevention of heart attacks.
Reason $(R)$: Aspirin acts as an anti-blood clotting agent.
The correct answer is:

• A
  Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$.
• B
  $A$ is correct and $R$ is not correct.
• C
  Both $A$ and $R$ are correct and $R$ is not the correct explanation of $A$.
• D
  $A$ is incorrect and $R$ is correct.