Short answer D <<<< Dilation means you go from one diagram to another. which direction (the figure increases or the figure decreases in size) is described by the scale factor. In this question the scale factor is greater than 1. The figure is getting bigger. so radius * scale factor = 2 * 4 = 8 is the answer.
If the question save dilated by a scale factor of 1/4 then the answer would have been 2 * 1/4 = 2/4 = 1/2
