Why is it useful to allow enough drying time between acrylic layers?

Correct answer: To prevent unwanted mixing with the lower layer

The governing concept is controlled layering. Acrylic forms a separate film as it dries, so allowing the lower layer to become sufficiently dry helps the next layer remain clean, sharp, and visually distinct. Applying a new wet layer too soon can disturb, lift, or unintentionally mix with the layer beneath. Drying does not turn acrylic into oil, change the canvas colour by itself, or harden the brush. Therefore option B is correct.