An observer moves towards a stationary source of sound with a speed 1/5^th of the speed of sound. The wavelength and frequency of the source emitted are $\mathrm{\lambda }$ and f respectively. The apparent frequency and wavelength recorded by the observer are respectively

• A

  $1.2\mathrm{f},\mathrm{\lambda }$

• B

  $\mathrm{f},1.2\mathrm{\lambda }$

• C

  $0.8\mathrm{f},0.8\mathrm{\lambda }$

• D

  $1.2\mathrm{f},1.2\mathrm{\lambda }$