Why should the lid of acrylic colour be closed after use?

Correct answer: To prevent the paint from drying quickly

The governing storage principle is to limit air exposure after a water-based acrylic product has been opened. Closing the lid reduces evaporation and helps keep the paint workable for its next use, so option D is correct. The lid does not make the container heavier, change the colour, or dry a brush. A tightly closed container also helps prevent a skin or hardened layer from forming on the paint.