Read the assertion and reason carefully to mark the correct option out of the options given below: Assertion: HIV causes cellular immunodeficiency. Reason : HIV kills both B ? lymphocytes and helper T ? lymphocytes.

• A. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
• B. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
• C. If the assertion is true but the reason is false
• D. If both the assertion and reason are false
• E. If the assertion is false but reason is true