A tint is a mixture with White, so C.
Symbolic proportion is the deliberate emphasis of objects in a work of art based on its importance as a symbol. This can sometimes also mean that in an artwork where symbolic proportion is applied, religious figures tend to be "bigger" or more emphasized compared to any other element a person may see in the piece.
The artist may have used symbolic proportion to emphasize the importance or prominence of Mary and Jesus Christ - this may be relative to any smaller objects around them in the scene.
Because art is a symbol or status of living. rural cultures out in the middle of nowhere fighting to survive don't have time or resource to create something. but rich countries or cultures with money to blow have no problem spending on something cool they can create. plus it shows the world a bit of that countries style and flavor
They demonstrate the central role that religion played in the lives of the Mesopotamians.