Final answer:
Point A at (-4,3) when reflected across the y-axis results in point B with coordinates (4,3), matching option A.
Step-by-step explanation:
When reflecting a point across the y-axis in a Cartesian coordinate system, the x-coordinate of the point changes sign, while the y-coordinate remains the same. Given the original point A with coordinates (-4,3), reflecting this point across the y-axis changes the x-coordinate from -4 to 4 while the y-coordinate remains at 3.
The reflected point B is thus at (4,3), matching option A. This process is known as reflection symmetry in the context of Cartesian planes.