The equation \( \arg \left( \frac{z-1}{z+1} \right) = \frac{\pi}{4} \) represents a circle with:
centre at \( (0,0) \) and radius \( \sqrt{2} \)
centre at \( (0,1) \) and radius \( \sqrt{2} \)
centre at \( (0,-1) \) and radius \( \sqrt{2} \)
centre at \( (0,1) \) and radius \( 2 \)