The displacement y of a particle in a medium can be expressed as ${\text{y=10}}^{\text{-6}}\text{sin}\left(\text{100t+20x+}\frac{\text{π}}{\text{4}}\right)\text{\hspace{0.17em}m}$  where t is in second and x in metre. The speed of the wave is

• A

  $2000{\text{\hspace{0.17em}m\hspace{0.17em}s}}^{\text{-1}}$

• B

  $5{\text{\hspace{0.17em}m\hspace{0.17em}s}}^{\text{-1}}$

• C

  $20{\text{\hspace{0.17em}m\hspace{0.17em}s}}^{\text{-1}}$

• D

  $5{\text{π\hspace{0.17em}m\hspace{0.17em}s}}^{\text{-1}}$