The correct answer is D. bituminous bound macadam.
Bituminous bound macadam is a type of road construction material that is made by mixing crushed stone with asphalt. It is a strong and durable material that is often used for base courses.
Bituminous carpet is a type of road construction material that is made by spraying a layer of asphalt onto a prepared surface. It is a relatively thin material that is often used for surface courses.
Mastic asphalt is a type of asphalt that is made with a high percentage of asphalt cement. It is a very sticky material that is often used for waterproofing and roofing applications.
Sheet asphalt is a type of asphalt that is made with a low percentage of asphalt cement. It is a relatively dry material that is often used for paving applications.
Bituminous bound macadam is the best choice for a base course because it is strong and durable. It is also a good choice because it is relatively inexpensive.