Two identical strings, a and b, have nearly the same tension. when they both 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. this means. a) that before and after tightening b has a higher frequency than that of ab) that before and after tightening a has a higher frequency than b. c) that before tightening b had a higher frequency than a, but after tightening, a has a higher frequency than b. d) that before tightening a had a higher frequecy than b, but after tightening. b has a higher frequency than a. e) none of the above.