Correct : a

Definition of Strongly Connected Component:
A strongly connected component (SCC) of a directed graph is a maximal set of vertices such that every vertex is reachable from every other vertex in the set.

Option A: G₁ is the complement of G.
The edges of G are removed and new edges are introduced, which can change the reachability between vertices. Therefore, the SCCs may change.

Option B: G₂ is the transpose of G, where every edge (u,v) in G becomes (v,u).
If there is a path from u to v in G, reversing all its edges gives a path from v to u in G₂. Thus, if u and v are mutually reachable in G, they are also mutually reachable in G₂, and vice versa.
Therefore, G and its transpose have exactly the same SCCs.

Option C: G₃ adds edges for paths of length 2. Adding such shortcut edges does not change reachability, because every new edge already corresponds to a path in G. Hence, C also preserves the SCCs.

Option D: G₄ removes isolated vertices. An isolated vertex itself forms an SCC, so removing it changes the set of SCCs.

Conclusion:
The standard and intended answer is:

Answer: (B) G₂ = (V,E₂) where E₂ = {(u,v) | (v,u) ∈ E}