This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following gives a positive reaction with Ferric chloridea) Phenylketonuriab) Alkaptonuriac) Maple syrup urine disease d) None 
Select and explain. 
A. ac, B. a, C. ad, D. ab
D: ab
Answer: D: ab 
Explanation: Ferric chloride test is positive in phenylketonuria and also in alkaptonuria.