the standard equation for circle is (x －h)² ＋(y －k)² = r² which h is the x coordinate, k is the y coordinate, r is radius. In this case, both x coordinate and y coordinate are 0, so the left side of the equation is x² + y², since the radius is √249, the r² is 249. So the equation is x² + y² = 249, and the answer is D.
