Consider the directed graph given below. Which one of the following is TRUE?

Let us analyze the dependencies (directed edges) in the given DAG:

• Edges from $P$: $P \to Q$, $P \to R$

• Edges from $S$: $S \to Q$, $S \to R$

• Edges from $R$: $R \to Q$

In-degrees of vertices:

• $\text{in-degree}(P) = 0$

• $\text{in-degree}(S) = 0$

• $\text{in-degree}(R) = 2$ (predecessors: $P, S$)

• $\text{in-degree}(Q) = 3$ (predecessors: $P, S, R$)

For a valid topological ordering:

1. Both $P$ and $S$ must precede $R$ and $Q$.

2. $R$ must precede $Q$.

Therefore, the first two vertices must be $P$ and $S$ in either order:

• If $P$ is first, then $S$ must follow before $R$, yielding: PSRQ.

• If $S$ is first, then $P$ must follow before $R$, yielding: SPRQ.

Thus, both PSRQ and SPRQ are valid topological orderings, making option (C) correct.