Why may choosing red yellow blue be incorrect when the question refers to a printing machine?

Correct answer: Printing uses cyan magenta and yellow as its base

The governing concept is context-dependent colour models. Most process printing uses subtractive CMY inks, commonly expanded to CMYK by adding black for better depth, text, and economy. Red, yellow, and blue are familiar traditional art primaries, but they are not the standard process-printing base set. Printing can reproduce red, so option D is false; it also does not use only black. Option A is correct.