34. HIV-1 protease is different from most mammalian aspartic acid proteases in that it has: (A) two subunits each with a two-aspartate active site. (B) two subunits each contributing an aspartate to the active site. (C) two active sites on one protein. (D) two subunits, one with an active site, and the other with a regulatory activity. (E) none of the above.