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: Medicine
Normal hea axis is: 
Select and explain. 
A. -90 to + 90deg, B. -90 to + 180deg, C. -30 to +90deg, D. -90 to 180deg
C: -30 to +90deg
Answer: C: -30 to +90deg 
Explanation: Answer is C (-30 to +90deg)