What will happen if fine trees are painted before the background wash dries?

Correct answer: The tree edges may spread

The governing concept is the difference between wet-on-wet and wet-on-dry application. If fine tree shapes are painted while the background wash is still wet, the new pigment follows the moisture and spreads outward. Branches and outlines therefore become soft or blurred instead of remaining sharp. This can be useful for misty effects, but it is unsuitable for delicate detail. Waiting until the wash dries gives better edge control, so option A is correct.