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: Forensic Medicine
In nonexposed persons, the level of coproporphyrin in urine is : 
Select and explain. 
A. Less than 150 microgram/litre, B. Less than 1000 microgram/litre, C. More than 500 microgram/litre, D. None of the above
A: Less than 150 microgram/litre
Answer: A: Less than 150 microgram/litre 
Explanation: A i.e. < 150 mg/litres