An oscilloscope is basically designed to convert:
A. visual signals to electrical signals
B. sound signals to electrical signals
C. electrical signals to visual signals
D. sound signals to visual signals

Hint: An oscilloscope (also known as scopes) is used to test and display varying voltage signals as waveforms, visual representations of the variation of voltage with respect to time. The oscilloscope basically shows the signals in the form of graphs which show how the signal is changing.

Complete step by step answer:
Let us discuss what an oscilloscope is.
An oscilloscope (also known as scopes) is used to test and display varying voltage signals as waveforms, visual representations of the variation of voltage with respect to time. The oscilloscope basically shows the signals in the form of graphs which show how the signal is changing.
There are various types of oscilloscopes such as analogue and digital. Earlier analogue oscilloscopes were used but as the technology became advanced in the field of electronics, digital oscilloscopes replaced the older ones.
Normally most oscilloscopes are easy to use and it helps to have an understanding of how these items of electronics theories and experiments work and instruments operate. Mostly soft keys are present on the screen, so there is a lot that can be done.
The main function of an oscilloscope is to display waveforms on some form of display like graphs. In these graphs, normally, the time is displayed along the horizontal axis (X-axis) and amplitude is displayed along the vertical axis (Y-axis). This makes it possible to easily study the waveforms and draw a conclusion.
Therefore, an oscilloscope is basically designed to convert electrical signals to visual signals.
Hence, option C is correct.

Note: Oscilloscopes have so many advantages and are an essential piece of any electronics laboratory for electronics test equipment. They are used in testing electronics hardware whether within RF design, basic electronics circuit design, electronics manufacturing, service, repair or anywhere that electronic circuits and the waveforms on them need to be observed.