$\int _{-1} ^ 1 \large\frac{\cos h x }{1+e^{2x}}$$dx$ is equal to :

Question

$$\begin {array} {1 1} (a)\;0 & \quad (b)\;1 \\ (c)\;\frac{e^2-1}{2e} & \quad (d)\;\frac{e^2+2}{2e} \end {array}$$