What can be mixed with brown to make light brown?

Correct answer: White

The governing concept is making a tint by increasing a colour’s lightness. Mixing white with brown raises its value and produces a lighter brown; the quantity should be added gradually so the desired shade is controlled. Therefore option B is correct. Black lowers value and makes brown darker, while blue or violet changes the hue rather than giving the simplest light-brown tint. This is a practical subtractive colour-mixing rule.