Solution
= Solution
\b[True.] Delete $e\in T$; the resulting two <connected components> define a <cut of a graph>. If a crossing edge $f$ had $w(f)<w(e)$, the exchange $T-e+f$ would be a <spanning tree> of smaller total weight, contradicting the <minimum spanning tree> assumption. Thus $e$ is a <light edge crossing a cut> for this fundamental cut. It need not be uniquely light.