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: Physiology
O2 consumption is minimal when temp. gradient between skin and external environment is: 
Select and explain. 
A. < 0.50deg, B. < 2.50deg, C. < 1.50deg, D. > 3.5deg
A: < 0.50deg
Answer: A: < 0.50deg 
Explanation: A < 0.5degC (still searching)