On the 12-lead ECG, extreme right axis deviation is characterized by:
A. a negative QRS in lead I and a negative QRS in lead aVF.
B. a positive QRS in lead I and a negative QRS in lead aVF.
C. a positive QRS in lead I and a positive QRS in lead aVF.
D. a negative QRS in lead I and a positive QRS in lead aVF.