A vehicle, with a horn of frequency n is moving with a velocity of 30 m/s in a direction perpendicular to the straight line joining the observer and the vehicle. The observer perceives the sound to have a frequency `n + n_(1)`. Then (if the sound velocity in air is 300 m/s)
A. `n_(1)=10 n`
B. `n_(1)=0`
C. `n_(1)=0.1 n`
D. `n_(1)= -0.1 n`
