If a vertex is removed from the graph G, 2 cases are possible-
Case 1: remove 1 isolated vertex and you will left with 7 components.
case 2: just think, 1 vertex connected to 12 other vertices in a star form and other 7 vertices are isolated. now remove star vertex, and you will left with 12+7=19 vertices which are isolated, so 19 components.
So, option C.