In which situation is wet-on-wet blending more useful?

Correct answer: Creating soft colour transitions in skies or clouds

Wet-on-wet blending means placing one wet colour into another wet area. Because the moisture allows pigment to move and merge gradually, it is useful for soft transitions such as an open sky, mist, or clouds. It is not the best method for sharp geometric edges, fine lettering, or a controlled black outline, where a drier surface and precise brush control are preferred.