What should be done to lighten red without making the pink too pale?

Correct answer: Add a small amount of white to red

The governing concept is making a tint by gradually adding white pigment. A small amount of white raises the lightness of red and produces a brighter pink while preserving some colour strength, so option A is correct. A large amount of white can make the pink very pale; black lowers lightness and creates a shade, while green is complementary to red and may neutralise it into a dull or muddy mixture. Add white in small steps and test each step.