This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2018, Subject name: Medicine
ECG shows a mean axis of 90 degrees. In which of the following would be present the maximum voltage of R wave? 
Select and explain. 
A. III, B. I, C. aVF, D. aVL
C: aVF
Answer: C: aVF 
Explanation: Lead I = R wave taller than S = +ve Lead avF = R wave taller than S = +ve