Triangle RST has vertices R(6, 5), S(9, −4), and T(10, 1). Triangle RST has vertices R′(6, −5), S′(9, 4), and T′(10, −1).
Which transformation of triangle RST produced triangle RST?
a rotation of 90° clockwise around the origin
a rotation of 90° counterclockwise around the origin
a reflection across the y-axis
a reflection across the x-axis