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
Phenylpyruvic acids in the urine is detected by: 
Select and explain. 
A. Guthrie's test, B. VMA in urine, C. Gerhas test, D. Ferric chloride test
D: Ferric chloride test
Answer: D: Ferric chloride test 
Explanation: Ferric chloride test is a quantitative test for the detection of phenylketonuria; the addition of ferric chloride to urine give rise to a blue green colour in the presence of phenylketonuria. This colour is due to phenylpyruvate.