What is the PRIMARY difference between quick breads and muffins?

a$.$

Quick breads use yeast as a leavening agent, while muffins do not.

b$.$

Muffins are a type of quick bread, but quick breads are not muffins.

c$.$

Quick breads have a denser texture than muffins.

d$.$

There is no significant difference; they are essentially the same.