Two Identical Strings, a and B, Have Nearly the Same

Multiple Choice

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 3 Hz.When string B is tightened slightly, to increase the tension, the beat frequency becomes 6 Hz.This means:

A) that before tightening A had a higher frequency than B, but after tightening, B has a higher frequency than A
B) that before tightening B had a higher frequency than A, but after tightening, A has a higher frequency than B
C) that before and after tightening A has a higher frequency than B
D) that before and after tightening B has a higher frequency than A
E) none of the above