When we perform a 90º clockwise rotation about the origin, the coordinates of a point P(x,y) are transformed to P'(y,-x).
So, to plot figure C, i.e., figure A after that transformation, we need to identify the coordinates of its vertices and then transform them.
We have:
(2, 1) → (1, -2)
(4, 1) → (1, -4)
(0, -2) → (-2, 0)
(2, -2) → (-2, -2)
Now, plotting the new points and joining them, we obtain: