Antiviral therapy for the human immunodeficiency virus (HIV) usually consists of a protease inhibitor that inhibits what function?

A) viral exit of the newly formed virions by vial budding
B) viral fusion of the viral envelope with the host cell membrane
C) binding to the CD4 receptor on human immune cells
D) insertion of viral DNA into the host cell DNA
E) cleavage of polypeptide chains to make functional HIV viral proteins