Final answer:
The term 'sweep' refers to the movement of the displayed trace across the oscilloscope screen, which reflects changes in voltage over time. So, the correct answer is c. sweep.
Step-by-step explanation:
The movement of the displayed trace across the scope screen is known as the sweep. In an oscilloscope, the sweep is responsible for drawing the signal over time on the screen, allowing us to observe changes in the signal's voltage as a function of time.
A sweep is generated by a sweep generator, which controls how quickly the trace moves across the scope from left to right. This movement can usually be adjusted for various time scales to accurately measure different frequencies or time periods within a signal.
Thus, the correct answer is c. sweep.