The angle of inclination of the plane at which the body begins to move down the plane, is called

Angle of Friction:
The angle of friction is the angle at which a body just begins to move down an inclined plane. It represents the maximum angle at which a body can rest on the inclined plane without sliding down. It is determined by the coefficient of friction between the surfaces in contact.

Angle of Repose:
The angle of repose is the maximum angle at which a pile of granular material remains stable without sliding or collapsing. It is the natural angle formed by loose particles such as sand, gravel, or powders when poured onto a flat surface. The angle of repose depends on factors such as the size, shape, and cohesion of the particles.

While both angles relate to the stability of objects on surfaces, they describe different scenarios: the angle of friction pertains to solid bodies on inclined planes, while the angle of repose relates to granular materials forming natural slopes.

Given the context of the question, which is about the angle at which a body begins to move down an inclined plane, the correct answer remains Option A: Angle of friction.