Determine the correctness or otherwise of the following Asertion (a) and the Reason (r) Assertion : MTT assay is used to determine cell viability based on the principle of colour formation by DNA fragmentation. Reason : MTT assay is used to determine cell viability based on the colour development by converting tetrazolium soluble salt to insoluble salt.

• A. both (a) and (r) are true and (r) is the correct reason for (a)
• B. both (a) and (r) are true and (r) is not the correct reason for (a)
• C. (a) is true but (r) is false
• D. (a) is false but (r) is true