The number of pixels that can be displayed on the screen at one time is known as what? screen resolution. viewing angle. color depth. pixel density.

screen resolution

Explanation:

The screen resolution indicates the number of pixels that can be displayed at one time on a given screen. For example, it could be numbers like 1920x1080, 1600x900 and so on.

Viewing angle has nothing with the pixel count, although viewing port would.  Color depth concerns the number of colors you can display at one time.  Pixel density is the concentration of pixels, like in Apple's retina display, that increases the number of pixels in the screen, but that doesn't give you the information on how many there are.

the answer to your question would be something called hertz. the unit of measurement called a hertz, which is one cycle per second, is used to measure clock speed. within one cycle, your computer processes, refreshes, or updates itself to the changes that it is going through. in the case of computer clock speed, one hertz equals one tick per second. the clock speed of computers is usually measured in megahertz (mhz) or gigahertz (ghz)