病毒的吸附主要由病毒体表面的蛋白成分与敏感细胞表面的____结合所介导,而穿入一般由____和融合两种形式。
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两种病毒感染同一细胞时,一种病毒抑制另一种病毒增殖的现象称为____。
We'll need __________ opinion.
A. expert
B. an expert
C. expertise
D. an expertise
He gave his son some money for the __________ of his school books.
A. purchased
B. purchase
C. purchasing
D. purchaser