One evening, P and Q were talking to each other face to face. If P's shadow fell exactly to Q's right, then which direction was P facing?
Correct: A
In the evening, the sun is in the West. Therefore, all shadows fall towards the East.
P's shadow fell exactly to Q's right. This means Q's right side is East.
If Q's right side is East, then Q must be facing South (because if you face South, East is to your left and West is to your right).
P and Q are talking face to face. If Q is facing South, then P, who is facing Q, must be facing North.