Final answer:
The anhydrous ointment base is the oleaginous base, which contains no water and serves as a moisture barrier on the skin. Option d is correct.
Step-by-step explanation:
The ointment base that is anhydrous (meaning it does not contain water) is the oleaginous bases. Oleaginous bases are composed entirely of oil or hydrocarbon ingredients and do not contain any water. They are also known as hydrocarbon bases.
This type of base is used when the medication within the ointment needs to be entirely free of water, and they form a barrier on the skin which can prevent moisture loss. In contrast, water miscible bases can absorb water and are not anhydrous, oil-in-water emulsion bases (O/W) contain water dispersed in oil, and water-in-oil emulsion bases (W/O) also contain water, though the oil phase is continuous in this case.