[单选题]
A sound has a frequen /5 (vfure*.aj v;3xjujqkec0 cy of 1000 Hz. If a listener moves with a speed of ;jg8 ( r:uuhcto bl5q230 m/s away f82qb h;:(o5clujt g rurom the source, what is the frequency heard by the observer? (The sound speed is 340 m/s.)
A. $912 \; Hz$
B. $919 \; Hz$
C. $1000 \; Hz$
D. $1090 \; Hz$
