@ gshivam63 See We are calculating the cost of for v_{1} of graph G_{1}
which is a subgraph of G_{1}
and we know we can calculate cost for connected edges only
Here G_{1} is subgraph of G , which must be connected.
But G can be disconnected.
A) is not true because we are calculating shortest path for every subgraph G_{1} ,not for G always . As G can be disconnected.
If u have any better example, u can give