Suppose, if each vertex is a component, then k=n, then there will not be any edges among them.
Now, replace the same concept in options,
Option 1 and 2: Both will give answer 1. (i.e. one edge among them) which is false.
Option 3: n-k = 0 edges.
Option 4: n-k+1 : 1 edge, which is false.