Two identical strings, A and B, have nearly the same tension. When theyboth vibrate in their fundamental resonant modes, there is a beat of 3Hz. When string B is tightened slightly, to increase the tension, the beat frequency becomes 6 Hz. a. that before and after tightening B has a higher frequencythan that of Ab. That before and after tightening A has a higher frequencythan B. c. that before tightening B had a higher frequency than A, butafter tightening, A has a higher frequency than B. d. that before tightening A had a higher frequecy than B, butafter tightening. B has a higher frequency than A. e. none of the above.