Answer:
a reflection over the y-axis
Explanation:
When a point is reflected over the y-axis, the images forms where the y-coordinate remains the same while the x-coordinate is transformed to the opposite sign.
In this case, a point (x,y) transforms to (-x,y). From the coordinates given;
(-3,3) --------(3,3)
(-1,3)----------(1,3)
(-2,1)----------(2,1)
See attached plot of object points and image points.