For Assertion $A$ and Reason $R$:
Assertion $A$: Smoking increases blood pressure and heart rate.
Reason $R$: Nicotine stimulates the adrenal gland.

• A
  Both Assertion $A$ and Reason $R$ are true,and $R$ is the correct explanation of $A$.
• B
  Assertion $A$ is true and Reason $R$ is false.
• C
  Assertion $A$ is false and Reason $R$ is true.
• D
  Both Assertion $A$ and Reason $R$ are true,but $R$ is not the correct explanation of $A$.