Let G(V, E) be an undirected graph with l edges. Then the sum of degree of all vertices is equal to ______________.

Correct option is A

In graph theory, the sum of the degrees of all vertices in an undirected graph is always twice the number of edges. This is a consequence of the Handshaking Theorem, which states that: "In any undirected graph, the sum of the degrees of all vertices is equal to twice the number of edges."
This theorem applies because each edge in an undirected graph contributes exactly two to the total degree count—one for each endpoint of the edge.
Information Booster:
1. Understanding Degree in Graphs:
· The degree of a vertex in an undirected graph is the number of edges connected to it.
· For a graph with l edges, each edge connects two vertices, adding 1 to the degree count for each vertex.