Final answer:
The best option for Mercy when she needs a brief break is to lock her computer, ensuring her work and sensitive information remain secure and intact until she returns.
Step-by-step explanation:
When Mercy needs to step away from her computer for a few minutes to go to the bathroom, the best option for her is to use the lock function. This option is quick, secure, and allows her to return and resume her work without having to reopen programs or files. The shutdown option would close all her programs and turn off the computer, which is unnecessary for a short break.
The log off option would close all her sessions and might result in loss of unsaved work, which is also not ideal for a brief absence. Therefore, locking her computer is the most suitable choice as it will keep all her work and programs intact while ensuring that her sensitive information is protected during her absence.