You may use this blank grid to help you answer this question.

If you don't choose to print it out, a piece of graph paper would
be just as useful.

The list shows the coordinates of $\bigtriangleup RST$ and $\bigtriangleup R'S'T'$

R(-4,6), S(-4,9), T(-9,6)

R'(2,6), S'(2,9), T'(7,6) Which transformation maps $\bigtriangleup RST$ to $\bigtriangleup R'S'T'$
A. A $180^\circ$ clockwise rotation about the origin
B. A $90^\circ$ clockwise rotation about the origin
C. A reflection over the line $y=-1$
D. A reflection over the line $x=-1$