[填空题]
You are standing still. Wha 2srn zi2 la8 :gxlg6.3gitz9ct frequency ygk)4+*-b6d/ nsea7 imdl-is y, dhsh do you detect if a fire engine whose sire )ad +-skh * i/bsh,-ie dn7mds4l6yygn emits at 1550 Hz moves at a speed of 32 m/s
(a) toward you, Hz
(b) away from you? Hz