Correct answer - Option C.
In the mentioned graph,
n=6,
e = 15 (Maximum edges = 6C2)
and also, it is connected,
Therefore, we can infer that given Graph is K6 (Complete graph of 6 vertices).
Every complete graph is K-1 regular.
Thus, it is a 5- regular graph i.e degree of every vertex is 5.
For an Euler circuit to be present, every vertex should have a even degree, which is false in this case .
Therefore, option C is True.