Need typed solution only

3. For which n is there a graph on n vertices ouch as all vertices of different degrees?Prove the claim. 4.Let A be a neighborhood of the graph G on n vertices, n a 2. Prove that if G is consecutive, then n_1 k for . . . E = A. . 3;. 0 each two 1irer'tlcea I, j. k 1 1.3