Assertion (A) Human beings have 23 pair of chromosomes, one of which is the sex chromosomes and the remaining are 22 autosomes. The X-linked disease are related to mutation on a sex chromosomes.
Reason (R) Colour blindness results from a mutation in X-chromosome.

A. Both A and R are true and R is the correct explanation of A

B. Both A and R are true, but R is not the correct explanation of A

C. A is true, but R is false

D. A is false, but R is true

Answer: Option B