Assertion (A): In pernicious anaemia, the size of RBC decreases, but their number increases in blood. Reason (R): It is caused due to deficiency of vitamin B₁₂.

Directions: In the following question, there are two statements: Assertion (A) and Reason (R). Consider both the statements independently and mark your answer as

1. if A and R both are correct and R is correct explanation of A
2. if A and R both are correct and R is not correct explanation of A
3. if A is correct and R is incorrect 
4. if A is incorrect and R is correct 
5. if A and R both are incorrect