[单选题]
A sound source departq/zw,p (n-gx cwd7bx (s from a statioug5dsvu mc 1m )u8 scle:5l;;znary observer. The frequency heard by the obs:;l)v mdcmu u1sg;sc85z eul 5erver is
A. higher than the source.
B. lower than the source.
C. the same as that of the source.
D. equal to zero.
