Which of the following is not a valid Red Book rating A A1 B

Which of the following is not a valid Red Book rating?

A. A1

B. B2

C. C1

D. C2

Solution

Option A. The reason is as follows : Red book uses B2 to denote Good , C2 for Fair and C1 for Minimum and another rating is also used which is None. Since question asks for a not valid rating, A is the answer.