So first of all we need to list the three points A, B and C so we can properly calculate the transformation:
The first transformation we have to perform is a 90° clockwise rotation about the origin. If we perform this rotation on a point (x,y) we get:
Then we apply this to A, B and C:
Then we must perform a reflection over the x-axis on the points of triangle A'B'C'. A reflection over the x-axis is achieved by applying this transformation:
If we transform points A', B' and C' with this we get:
Then if we graph all the three triangles in the same grid we get the following picture:
As you can see this image is the same as the one in option D. This means that the answer to this question is graph D.