This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Mechanical injuries, Subject name: Forensic Medicine
Black scab is formed at 
Select and explain. 
A. 4-5 days, B. 6-7 days, C. Less than 24 hours, D. After 7-10 days
B: 6-7 days
Answer: B: 6-7 days 
Explanation: Age of abrasion Less than 24 hours bright red - reddish scab 2-3 days reddish- brown scab 4-5 days dark brown scab 6-7 days black scab ref: FORENSIC MEDICINE AND TOXICOLOGY Dr PC IGNATIUS THIRD EDITION PAGE 114