smc

We know that the formula for slope is $m=\frac{y_2-y_1}{x_2-x_1}$ We are give the points $(m,3)$ and $(1,m)$. Substituting into the slope formula, we get $\frac{m-3}{1-m}$ After taking the cross-products and solving, we get $\sqrt{3}$, which is answer choice $\boxed{\sqrt{3}}$.