How should a watercolour brush be kept after washing?

Correct answer: Reshape the bristles and dry it horizontally

The governing concept is proper brush maintenance. After washing, the bristles should be gently reshaped and the brush should dry horizontally, preferably in a clean, ventilated place. Thus, option B is correct. This position prevents water from collecting near the ferrule and helps preserve the pointed shape. Standing it in paint, pressing the bristles down, or sealing it in a wet box can bend, weaken, or spoil the brush.