Final answer:
Reflecting point B across the y-axis will result in it being in either Quadrant II or III if it originally lay in Quadrant I or IV, respectively, and vice versa.
Step-by-step explanation:
If you were to reflect point B across the y-axis, the quadrant in which it would be located depends on its original position. Points to the right of the y-axis are in Quadrants I and IV, and when reflected across the y-axis, they would move to Quadrants II and III, respectively. Similarly, if point B starts in Quadrant II or III (to the left of the y-axis), the reflection across the y-axis would place it in Quadrant I or IV.
For example, if point B is in Quadrant I, reflecting it across the y-axis would place it in Quadrant II, which is horizontal to the left of the coordinate system. If point B is in Quadrant IV, reflecting it across the y-axis would put it in Quadrant III, again to the left side of the coordinate system.