Which HIV entry inhibitor is administered orally?

The correct choice is Maraviroc, which is an HIV entry inhibitor administered orally. Maraviroc works by blocking the CCR5 co-receptor on the surface of T-cells, which prevents HIV from entering these cells. This action is crucial for inhibiting the progression of the HIV infection, as it specifically targets the virus's ability to infect immune cells.

In contrast, Enfuvirtide is a fusion inhibitor that must be administered by subcutaneous injection rather than orally, as its formulation is designed for direct delivery into the bloodstream. Rilpivirine, while an antiviral drug used in HIV therapy, is a non-nucleoside reverse transcriptase inhibitor rather than an entry inhibitor, which is outside the context of this specific question regarding entry inhibitors. Raltegravir is an integrase strand transfer inhibitor, also not an entry inhibitor, and is typically taken orally but does not fit the specific mechanism of action required for this question. Thus, the choice of Maraviroc as an oral entry inhibitor is substantiated by its specific targeting of the entry process of HIV into host cells.