Question

question 1-50
which is a feedback mechanism for a system?
the progress bar when downloading a file on itunes
the center scroll wheel on a computer mouse
the temperature setting knob on a refrigerator
the power button on a computer monitor

Explanation:

A feedback mechanism provides information about the state or progress of a system. The progress bar when downloading a file on iTunes shows the progress of the download, giving information back to the user about the system's operation. The center scroll - wheel is an input device, the temperature - setting knob is also an input for setting a value, and the power button is an on/off control, none of which are feedback mechanisms.

Answer:

the progress bar when downloading a file on iTunes