Consider the relation $X(P,Q,R,S,T,U)$ with the following set of functional dependencies
$F = \{ \\ \; \; \{P, R\} \rightarrow \{S, T\}, \\ \; \; \{P, S, U\} \rightarrow \{Q, R\} \\ \; \}$
Which of the following is the trivial functional dependency in $F^+$, where $F^+$ is closure to F?
- $\{P, R\} \rightarrow \{S, T\}$
- $\{P, R\} \rightarrow \{R, T\}$
- $\{P, S\} \rightarrow \{S\}$
- $\{P, S, U\} \rightarrow \{Q\}$