What can be done to create a highlighted area in an acrylic painting?

Correct answer: Add white to the base colour

The governing concept is value modelling: a highlight is a lighter area that receives or represents stronger light. Mixing white with the base colour raises its value and creates a controlled highlight, especially when the light source is kept consistent across the object. Black would create a darker value, erasing removes the painted form, and sand changes texture rather than producing ordinary light. Therefore, option C is correct.