What will you adjust in this experiment, so an exact number of half wavelengths fit on the string?

Group of answer choices

the frequency, since the frequency and wavelength are inversely proportional

the effective length of the string, since that changes what half wavelength$($s$)$ will fit on the string

the tension in the string, since that changes the wave velocity and thus the wavelength

room temperature and thus string temperature, since that changes the wave velocity and thus the wavelength