# S1: Radio waves can be polarized.  S2: Sound waves in air are longitudinal in nature.
$\begin {array} {1 1} (a)\;\text{S1 and S2 are true; S2 is a correct explanation of S1.} \\ (b)\;\text{S1 and S2 are true; S2 is not a correct explanation of S1.} \\ (c)\;\text{S1 is true; S2 is false}\\ (d)\;\text{S1 is false; S2 is true.} \end {array}$