Q.15.19 (d) Explain why (or how) :
(d) solids can support both longitudinal and transverse waves, but only longitudinal waves can propagate in gases,
Transverse waves produce shear, gases don't have shear modulus and cannot sustain shear and therefore can only propagate longitudinal waves. Solids have both shear and bulk modulus of elasticity and can propagate both transverse and longitudinal waves.