The integral $\oint_{c}^{ } (ydx-xdy)$ is evaluated along the circle $x^2+y^2=\frac{1}{4}$ traversed in counter clockwise direction. The integral is equal to

1. $0$
2. $\frac{-\pi }{4}$
3. $\frac{-\pi }{2}$
4. $\frac{\pi }{4}$