Evaluate the Integral $\int_{0}^{1 / 2} \frac{4 d r}{\sqrt{1-r^{2}}}$ A) $\frac{\pi}{4}$ B) $\frac{1}{5}$

Multiple Choice

Evaluate the integral. $\int_{0}^{1 / 2} \frac{4 d r}{\sqrt{1-r^{2}}}$

A) $\frac{\pi}{4}$
B) $\frac{1}{5}$
C) $\frac{\pi}{5}$
D) $\frac{1}{4}$
E) $\frac{2 \pi}{3}$