Let's analyze the movements of each individual based on the starting positions at the corners of a square field.
Assume the square is oriented with its sides parallel to the cardinal directions (North, South, East, West):
- A starts at the bottom left corner and moves North, placing him at the top left corner.
- B starts at the bottom right corner, moves East, but then returns to his original position. Thus, B remains at the bottom right corner.
- C starts at the top right corner and walks two sides anticlockwise. Moving anticlockwise, C first goes to the top left corner (1st move), then to the bottom left corner (2nd move).
- D remains at the top left corner as no movement is described for D.
After all movements:
- A is at the top left corner.
- B is at the bottom right corner.
- C is at the bottom left corner.
- D is at the top left corner.
From the positions noted, B is at the bottom right corner and C is at the bottom left corner, making them diagonally opposite.
Thus, the correct position is: B & C are diagonally opposite positions.