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
55 years old male, known smoker complains of pain in calf on walking. pain still persists on continuing walk, but can walk with effort. which grade of claudication does this patient fall under 
Select and explain. 
A. Grade I, B. Grade II, C. Grade III, D. Grade IV
B: Grade II
Answer: B: Grade II 
Explanation: Boyd's classification of claudication :
Grade I : Pian on walking, that improves with further walking.
Grade II : pain on walking, but patient continues to walk with pain.
Grade III : Pain on walking, that compels patient to take rest.
Grade IV : Rest pain.