动物注射活病毒疫苗后使机体获得免疫保护作用,这属于()。
A.人工主动免疫
B.人工被动免疫
C.天然被动免疫
D.天然主动免疫
E.非特异性免疫
参考答案:A
Many good suggestions were _______ at the meeting to cheer up teenagers to be more confident.
A.added to
B.figured out
C.got across
D.put forward
以下哪些词不宜出现在论文标题中()
A.研究
B.探讨
C.初探
D.作用