S1
let P(x) be "x is a priest" and Q(x) be "x is purified"
then S1 will be "If someone is priest then everyone is purified $\Rightarrow$ If everyone is priest then everyone is purified"
Valid because if premises("If someone is priest then everyone is purified") is true then Conclusion will be true because it states everyone is priest hence they are purified.
S2
let H(x) be "x is happy" and M(x) be "x is watching a movie"
$\left \{ \exists x H(x),\forall x (H(x) \rightarrow M(x) \right \} \rightarrow \forall x M(x)$
$\left \{ \exists x H(x) \wedge \forall x (H(x) \rightarrow M(x)) \right \} \rightarrow \forall x M(x)$
this is a Not valid because if premises is true then conclusion can be false
For premises to be true let's assume someone is happy and not everyone is happy then also premises is true
$\left \{ True \wedge \forall x (False \rightarrow M(x)) \right \} \rightarrow \forall x M(x)$
and Let $\forall x M(x)$ be False
$\left \{ True \wedge True \right \} \rightarrow False$
Hence A) Only S1 is Valid
