The displacement of particles in a string stretched in the x-direction is represented by y. Wave equation is described by :

• A

  cos kx sin wt

• B

  ${\mathrm{k}}^2{\mathrm{x}}^2 – {\mathrm{w}}^2{\mathrm{t}}^2$

• C

  ${\cos }^2(\mathrm{kx} + \mathrm{wt})$

• D

  $\cos ({\mathrm{k}}^2{\mathrm{x}}^2 – {\mathrm{w}}^2{\mathrm{t}}^2).$