Assertion (A): Persons suffering from alkaptonuria excrete urine that turns black on exposure to air.

Reason (R): This is due to presence of a substance Alkapton (homogentisic acid) in their urine.

[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 & Explanation
Answer: Option [A]