[单选题]
A sound source departs from a s-,xt:hg x 3lf/gne 2 qc-zxbj9ta4g9p ;fwros)p3ukuue f857 kmtionary observer. The frequency heard by the o 784r)ws ufopf3; u5epg9km kubserver is
A. higher than the source.
B. lower than the source.
C. the same as that of the source.
D. equal to zero.
