Assertion : IgM is a type of immunoglobulin which cannot cross the placenta. Reason : IgM is pentamer immunoglobulin, joined by J-chain.

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