What technique did egyptian artist use to paint their relief carvings ?

C. Polychrome

Explanation:

Polychrome is the art of painting or decorating with many colors bidimensional works as well as certain parts of tridimensional works. It can relate to the practice of decorating architectural elements, sculptures, reliefs, etc., in a variety of colors.Egyptian reliefs were usually carved before being painted. There are 2 primary classes of reliefs, raised and sunk reliefs. The surface would be smoothed with a layer of plaster and then painted.

the longest time is 123 years