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[主观题]
Which of the following is true according to the passage? [A]Fluvaccinesnowmainlyus
Which of the following is true according to the passage?
[A] Flu vaccines now mainly use egg-based technology.
[B] A bird influenza has once circulated among humans.
[C] Safety can be greatly improved with cell-culture vaccines.
[D] Modern vaccine production methods are to replace egg-based methods.
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