What is the best solution if a thick acrylic layer is taking too long to dry?

Correct answer: Apply thin, even coats of paint next time

The governing concept is controlled layer thickness and uniform drying. A heavy acrylic deposit can remain wet underneath even when its surface begins to dry, so adding another thick coat makes the problem worse. The best preventive solution is to build colour gradually with thin, even coats and allow each layer to dry. Option D is therefore correct. Excess water may weaken coverage or the paint film, while folding paper is unrelated and can damage the work.