Which type of transformation must have occurred in order to map triangle RST to its image, triangle R’S’T’?

On a coordinate plane, triangle S T R has points (negative 3, 3), (negative 1, 3), (negative 2, 1). Triangle S prime T prime R prime has points (3, 3), (1, 3), (2, 1).
a reflection over the y-axis
a translation to the right
a translation to the left
a clockwise rotation

a reflection over the y-axis

Step-by-step 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.