When you are talking to someone and you want a certain phrase you said to stand out, you emphasis your words. That is pretty much the same case here. A is incorrect because that is capturing a model of some sort, B is incorrect because that would be an equal blend of all colors together, and D is incorrect because you are not uniting the colors, you want the elements to stand out. Emphasis is achieved usually by using mostly dark colors then a splash of something such as neon pink or yellow.
This is a true statement. The dictionary definition of "synthesizer" is "an electronic musical instrument, typically operated by a keyboard, producing a wide variety of sounds by generating and combining signals of different frequencies."
A circle?? I am not sure. Sorry if it is wrong
