Antigenic shift refers to the combination of two different strains of influenza; in contrast, antigenic drift refers to the natural mutation of a single strain of influenza.
A. influenza; in contrast, antigenic drift refers to the natural mutation of a single strain of influenza
B. influenza, different than the natural mutation of a single strain, known as antigenic drift
C. influenza, in contrast to the natural mutation of a single strain, known as antigenic drift
D. influenza, different than antigenic drift, which refers to the natural mutation of a single strain of influenza
E. influenza; in contrast to antigenic drift, which refers to the natural mutation of a single strain of influenza
其它选项都知道错在哪,C选项是不是用Agentina shift与 the natural...进行比较了?怎样改就对了?
-- by 会员 yexianda (2013/1/7 13:25:35)