Which of these fits gap 21?

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.

The white light that we see around us is a ______(21)_____mix of seven colours, that if divided and laid side by side for study make up a light spectrum. The seven colours are Violet, Indigo, Blue, Green, Yellow, Orange and Red. However, Blue, Green, and Red are the _____(22)______ colours, because all the other colours may be got by mixing these. We think that a cherry is red because we see it_____(23)_____ a red colour. However, if we applied a filter and ____(24)_______the red part of the light from its source, then the cherry would appear black.