Why does using a small brush for a large wash increase the chance of streaks?

Correct answer: More strokes and joins are required

The governing concept is matching brush capacity and width to the area being painted. A small brush covers less surface and carries less liquid, so a large wash requires many separate strokes and joins. Those joins may begin drying at different times, creating visible bands or streaks. Option C is correct. Brush size does not automatically determine colour darkness, and a small brush can hold water and be used for wet paint.