Two musicians are comparing their trombones. The first produces a tone that is known to be 438 Hz. When the two trombones play together they produce 6 beats every 2 seconds. Which statement is true about the second trombone?
(a) It is producing either a 432-Hz sound or a 444-Hz sound.
(b) It is producing either a 436-Hz sound or a 440-Hz sound.
(c) It is producing a 444-Hz sound, and could be producing no other sound frequency.
(d) It is producing either a 435-Hz sound or a 441-Hz sound.
(e) It is producing a 441-Hz sound and could be producing no other sound frequency.