Two graphs of the same harmonic wave are shown below. The graph (1) on the left shows the displacement of wave y, as a function of position x for a given instant of time. The graph ( 2 ) on the right shows the displacement of wave as a function of time 't' for a given position. The speed of the wave is

• A

  $5.0 \mathrm{cm} {\mathrm{s}}^{-1}$

• B

  $0.5 \mathrm{cm} {\mathrm{s}}^{-1}$

• C

  $0.4 \mathrm{cm} {\mathrm{s}}^{-1}$

• D

  $4.0 \mathrm{cm} {\mathrm{s}}^{-1}$