Dredge-Ups Occur When Convection Extends from Deep Within a Star

Dredge-ups occur when convection extends from deep within a star to the surface. Three of the following examples of deep convection can dredge up heavy elements to the surface. Which example does NOT dredge up heavy elements?

A) Convection in a red dwarf starts in the core.
B) Convection starts deep within a star when it becomes a red giant for the first time.
C) A dredge-up occurs when a star first becomes an asymptotic branch star.
D) For stars more massive than about 2 M ? , a dredge-up occurs late in the asymptotic branch period.