To solve the problem, let's analyze the given transformation:

1. Reflection across the y-axis:
   When a point $(x, y)$ is reflected across the y-axis, its x-coordinate changes sign while the y-coordinate remains the same. The transformation rule is: $(x, y) \to (-x, y)$

2. Verify the options:

   • A. $(x, y) \to (x, -y)$: This describes a reflection across the x-axis, not the y-axis.
   • B. $(x, y) \to (-x, y)$: This matches the rule for reflection across the y-axis.
   • C. $(x, y) \to (y, -x)$: This is a 90-degree clockwise rotation.
   • D. $(x, y) \to (-y, x)$: This is a 90-degree counterclockwise rotation.

3. Correct Answer:
   The rule that describes the transformation is B. $(x, y) \to (-x, y)$.

Would you like a more detailed breakdown of how the coordinates change or further explanation on transformations?

Related Questions:

1. What is the rule for reflecting a point across the x-axis?
2. How do you find the new coordinates after a 180-degree rotation?
3. What is the effect of reflecting a shape across the origin?
4. How do transformations affect the area and shape of a figure?
5. Can a reflection be combined with other transformations to achieve specific effects?

Tip:

When reflecting across an axis, always focus on the coordinate that changes sign—the x-coordinate changes for a y-axis reflection, while the y-coordinate changes for an x-axis reflection.