What is the primary function of a video card in relation to CRT?

The primary function of a video card in relation to a CRT (Cathode Ray Tube) display primarily involves the conversion and manipulation of signals for effective display. In this case, the correct answer points to the video card's role in mixing and amplifying video signals, which is essential for producing the visuals shown on a CRT monitor.

Video cards take input data from the computer and convert it into a format that can be displayed on the screen. For CRT displays, the video card needs to ensure that the analog video signal is compatible with the CRT technology, which operates by controlling the electron beam that scans across the display screen, illuminating phosphor dots to create images. This process requires an appropriate mix and amplification of the video signals to maintain image quality and clarity, particularly at various resolutions and refresh rates.

While there are other functions associated with video cards, such as rendering 3D graphics or dealing with audio signals, these are secondary in the context of the traditional role they play regarding CRT displays. The correct answer highlights the core function that aligns with how CRT technology operates, emphasizing the importance of proper video signal processing in generating the final image output.