The correct answer is: A. flicker and slow update.
A raster CRT is a type of cathode ray tube (CRT) that uses a raster scan to display an image. This means that the image is drawn line by line, from top to bottom. This eliminates the flicker that is often seen on older CRTs, which used a non-interlaced scan.
A raster CRT also eliminates the slow update that is often seen on older CRTs. This is because the image is drawn line by line, rather than all at once. This allows the image to be updated more quickly, which results in a smoother image.
Option B is incorrect because it only mentions slow update. Option C is incorrect because it only mentions flicker. Option D is incorrect because it states that the raster CRT has no effect. Option E is incorrect because it is not one of the possible answers.