[单选题]
A vibration generatooz8ydm* jb,a cv; p5g6r with a freqbo4w owhip12ke,)2 t 8hfjdndu2- ai8 uency of 5Hz produces a travelling wave in a string. The graph shows how displacement of particles in the string varies with the distance from t)ouf2 ,4eiw 8w dnik-pbdo hj12ha 2t8he source.
What is the wavelength and the speed of the wave?
A. Wavelength 5cm;Speed 25 $cms^{-1}$
B. Wavelength 5cm;Speed 1 $cms^{-1}$
C. Wavelength 5mm;Speed 25 $cms^{-1}$
D. Wavelength 5mm;Speed 1 $cms^{-1}$
