In?uenza Virus Can Exhibit Constant Mutation of Viral Glycoproteins, Called

Multiple Choice

In?uenza virus can exhibit constant mutation of viral glycoproteins, called antigenic ________, or alternatively antigenic ________, which is a more serious phenomenon caused by the exchange of a viral gene with that of another in?uenza virus strain.

A) drift; exchange
B) exchange; drift
C) drift; shift
D) shift; drift