P, Q, R and S are four metals with the following reactions. Only Q and R react with dilute hydrochloric acid to give hydrogen. When Q is added to a solution containing ions of the other metals, metallic P, R and S are formed. P reacts with concentrated nitric acid but S does not. The correct order of their reducing character is

$$S<P<R<Q$$

$$S<R<P<Q$$

$$R<Q<P<S$$

$$Q<P<S<R$$