For stringed instruments, frequency is given by:

$\overline{){\mathbf{f}}{\mathbf{=}}\frac{\sqrt{{\displaystyle \frac{\mathbf{F}}{\mathbf{m}}}}}{\mathbf{2}\mathbf{L}}}$

Where F is the tension force on the string, L is the length of the string, and m is the linear mass density, also referred to as mass per unit length.

In a stringed musical instrument, the sound frequency of a particular string can be increased by

A. lengthening the string.

B. loosening the string.

C. tightening the string.

D. increasing the string's thickness.