A vehicle , with a horn of frequency `n` is moving with a velocity of `30 m//s` in a direction prependicular to the straight line joining the observer and the vehicle . The observer perceives the sound to have a grequency `(n + n_(1))` . If the sound velocity in air is `330 m//s` , then
A. `n_1=10n`
B. `n_1=-n`
C. `n_1=0.1n`
D. `n_1=0`