Consider a directed graph with $n$ vertices and $m$ edges such that all edges have the same edge weights. Find the complexity of the best-known algorithm to compute the MST of the graph?
A. $\mathbf{O}(\mathrm{m}+\mathrm{n})$
B. $O(m \log n)$
C. $\mathrm{O}(\mathrm{mn})$
D. $O(n \log m)$