有包膜的病毒侵入宿主细胞的方式是（）
A.胞饮
B.吞噬
C.受体介导的内吞作用
D.膜融合
E.直接穿入
参考答案：D
Tom's parents were not happy about his grade in the examination, _____. [ ]
A. he himself was neither
B. neither was he himself
C. he himself was either
D. either was he himself
要求完好保存多种抗原活性时选择（）
A.冰冻切片
B.石蜡切片
C.振动切片
D.塑料切片
E.包埋切片
