The area of the shaded region in the figure given below is

Answer: Option C

Area of shaded region = Area of semicircle - Area of triangle
$$\begin{array}{rl}& =\frac{\pi {\left(a\right)}^2}{2}-\frac{1}{2}\times a\times 2a\\ & =\frac{\pi a^2}{2}-a^2\\ & =a^2\left(\frac{\pi }{2}-1\right)\text{ sq}\text{. units}\end{array}$$