Question 16The figure shown is the union of a circle and two semicircles of diameters $a$ and $b,$ all of whose centers are collinear. The ratio of the area of the shaded region to that of the unshaded region is $\sqrt{\frac ab}$$\frac ab$$\frac{a^2}{b^2}$$\frac{a+b}{2b}$$\frac{a^2+2ab}{b^2+2ab}$
