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: Surgery
According to Boyd classification of intermittent Claudication; Rest pain is seen in 
Select and explain. 
A. Grade 1, B. Grade 2, C. Grade 3, D. Grade 4
D: Grade 4
Answer: D: Grade 4 
Explanation: None