![Which of the following is true according to the passage? [A]Fluvaccinesnowmainlyus](http://www.mshxw.com/aiimages/29/23021.png "Which of the following is true according to the passage? [A]Fluvaccinesnowmainlyus")
Whichofthefollowingistr ueaccordingtothepassage?
[A]Fluvaccinesnowmainlyuseegg-basedtechnology.
[B]Abirdinfluenzahasoncecirculatedamonghumans.
[C]Safetycanbegreatlyimprovedwithcell-culturevaccines.
[D]Modernvaccineproductionmethodsaretoreplaceegg-basedmethods.
正确答案：A
