[单选题]
A train is traveling away from /myyz .-ryoz .7xdfb 5yoquz2-ndfvp2 ,u at 120 km/h. It blows its whistle, and you hear a tone of 400 Hz. Take the speed of sound t f z22qduvp,-no be 340 m/s. What is the actual frequency of the whistle?
A. $444 \; Hz$
B. $439 \; Hz$
C. $364 \; Hz$
D. $361 \; Hz$
