If $\tan\alpha=\large\frac{x}{x+1}$ and $\tan \beta=\large\frac{1}{2x+1}$ then $\alpha+\beta$ is

Question

$(a)\;0\qquad(b)\;\large\frac{\pi}{4}$$\qquad(c)\;\large\frac{\pi}{3}$$\qquad(d)\;\large\frac{\pi}{2}$