A new vaccine for the upcoming flu season is developed from an influenza isolate designated A/Shanghai/2/2013(H7N9). This nomenclature means the isolate is

A) a type A with antigens HA 7 and NA 9 isolated in Shanghai in February 2013.
B) a type A with 7 HA antigens and 9 NA antigens isolated in Shanghai in February 2013.
C) the second type A strain with HA 7 and NA 9 antigens isolated in Shanghai in 2013.
D) a type B strain with antigens HA 7 and NA 9, first isolated in February 2013.
E) a hybrid of 2 type As combining 7 HA and 9 NA antigens, created in February 2013.