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
Which of the following is the hallmark of chronic renal failure? 
Select and explain. 
A. Metabolic acidosis, B. Hypercalcemia, C. Hypokalemia, D. Increased proneness to hypoxia
A: Metabolic acidosis
Answer: A: Metabolic acidosis 
Explanation: Metabolic acidosis (Ref: Robbin's 7th Ed/Pg 961) Manifestations of chronic renal failure: I. Fluid & electrolyte 1. Dehydration 2. Edema 3. Hyperkalemia 4. Metabolic acidosis II. Calcium, Phosphate, & bone 1. Hyperphosphatemia 2. Hypocalcaemia 3. Secondary hyperparathyroidism 4. Renal osteodystrophy III. Hematologic 1. Anemia 2. Bleeding disorders IV. Neuromuscular 1. Myopathy 2. Peripheral neuropathy 3. Encephalopathy V. Dermatological 1. Yellow colour 2. Pruritis 3. Dermatitis