(单选题)

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.

参考答案：A

参考解析：

细节理解题。根据第五段倒数第二句话“although the bug never circulated among humans.”可知禽流感没有在人类中传播，人类只是感染；故排除B；文中并未提到细胞培养的疫苗更加安全，也未提及现代疫苗生产会取代借助于食用鸡蛋的方式生产疫苗的方法，因此排除C、D。故选A。

知识点：阅读理解四选一英语专业基础知识阅读理解教师招聘-小学英语