Which statement correctly distinguishes subgrade, subbase, and base in pavement layers?

Which statement correctly distinguishes subgrade, subbase, and base in pavement layers?

• A. Subgrade is the in-situ soil; subbase is a drainage-stable granular layer; base is the stiff layer beneath the surface for load transfer.
• B. Subgrade is the surface wearing course; subbase is the intermediate asphalt; base is the subsoil layer.
• C. Subgrade is a drainage layer; subbase is soil; base is the in-situ rock.
• D. Subgrade and base are identical; subbase is only for water filtration.

Answer: (B)