What is the main principle of a stay-wet palette?

Correct answer: Maintain paint moisture through a damp base in a covered environment

The governing principle of a stay-wet palette is slowing evaporation from acrylic paint. A damp, absorbent layer beneath suitable palette paper supplies a humid environment, while a cover reduces exposure to moving dry air. This keeps the paint workable for longer, although it does not make it permanently wet. Heating and sunlight accelerate drying, and adding oil changes the medium rather than preserving it. Thus A is correct.