Question

what is the finished surface of the road foundation called?
center grade
subgrade
base grade
neutral grade

Explanation:

In road - building, the subgrade or subgrade soil layer is the finished surface of the road foundation. It provides a stable base for the layers above it. Center grade refers to the elevation at the center of the road, base grade is related to the base layer of the road structure, and neutral grade is not a standard term for the finished surface of the road foundation.

Answer:

B. Subgrade