Consider the following database table having A, B, C and D as its four attributes and four possible candidate keys (I, II, III and IV) for this table:A B C Da1 b1 c1 d1a2 b3 c3 d1a1 b2 c1 d2I: {B} II: {B, C} III: {A, D} IV: {C, D} If different symbols stand for different values in the table (e.g., d1 is definitely not equal to d2), then which of the above could not be the candidate key for the database table?

• A. I and III only
• B. III and IV only
• C. II only
• D. I only