What is the most likely reason if the lower layer lifts while applying a transparent glaze over dry paint?

Correct answer: The brush was rubbed too much

The governing concept is gentle layering in glazing. Even when the underlayer looks dry, repeated scrubbing, heavy pressure, or too many passes can rework the surface and lift or disturb the paint beneath. Thus option A is the most likely cause. Transparency itself does not lift paint, a light underlayer is acceptable, and brush size alone does not cause this failure.