Inhibition of the M2 protein of influenza with the drug amantadine will block which step of virus entry?

A) fusion of the viral envelope with the endosome membrane.
B) movement of the RNA genome segments through the nuclear pore
C) the conformational change that the HA proteins exhibit in response to the drop in pH
D) binding to sialic acid on the surface of the host cell
E) unpacking of the viral RNA genome segments from the virion