# If $f(x)=\left\{\begin{array}{1 1}\large\frac{1-\cos\lambda x}{x\sin x}&x\neq 0\\\large\frac{1}{2}&x=0\end{array}\right.$ is continuous at $x=0$ then $\lambda$ is
$(a)\;0\qquad(b)\;\pm 1\qquad(c)\;1\qquad(d)\;None\;of\;these$