![What step is essential to the traditional production of flu vaccine? [A]Manufactur](http://www.mshxw.com/aiimages/29/23055.png "What step is essential to the traditional production of flu vaccine? [A]Manufactur")
Whatstepisessentialtothetr aditionalproductionoffluvaccine?
[A]Manufacturersimplantthevaccineintoorderedchickeneggs.
[B]Scientistsidentifytheexactstr ainsoonafteraflupandemicstarts.
[C]Publichealthmeasuresaretakenasanimportantpandemic-fightingtool.
[D]Virusesaredeadenedandmadecleanbeforebeingputintovaccineuse.
正确答案：D
