A transverse wave is described by the equation $y=a\sin 2\pi \left(ft-\frac{x}{\lambda }\right).$ The maximum particle velocity is equal to four times the wave velocity if

• A

  $\lambda =\frac{\pi a}{4}$

• B

  $\lambda =\frac{\pi a}{2}$

• C

  $\lambda =\pi a$

• D

  $\lambda =2\pi a$