A T-switch is used to
Answer is D).
https://physics.ucsd.edu/neurophysics/Manuals/Inmac/Inmac%20An%20Applications%20Guide%20for%20Inmac%20T-Switches.pdf
Thanks for this reference. You can write this in a good way like this: https://physics.ucsd.edu/neurophysics/Manuals/Inmac/Inmac%20An%20Applications%20Guide%20for%20Inmac%20T-Switches.pdf