The most common was is your phone
Answer: Answer below.
Explanation:
I'm not fully sure myself, so don't agree with me fully.
I believe what she may have done wrong is tell the technician about a "program." A program doesn't have to do anything with physical hardware.
Operating System (OS) is the answer.
An application runs in/on an OS. It is not the OS itself. Like Word or Chrome are applications.
Systems is too generic and not specific enough to mean anything in this context. Throw away answer.
Network Operating System does not 'usually' run on a hard drive but on memory chips in things like routers, wireless access points and switches that move network traffic.
