Assertion : Foetal disorders can be diagnosed by chorionic villi sampling. Reason : Karyotyping can be done for mitotically dividing cells of chorionic villi.

• 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.