载体的功能是（I运送外源基因高效进入受体细胞II为外源基因提供复制能力III为外源基

单项填空

Tom wants to be______ engineer when he______ up.[ ]

A. an;grows

B. an;will grow

C. a;is growing

D. the;grow

使用抗生素治疗败血症时，下列做法正确的是（）

A.体温正常后1～3天方可停药

B.体温正常后7天即可停药

C.体温正常后7～10天再停药

D.体温正常后4周停药

E.体温正常后8周方可停药

退出投标是痛苦的选择，但以下哪项情况通常无法事先预知，只能中途退出（）

A.资质不符

B.有实力强于本方，每遇必败的对手介入

C.进行中，发现有预期更好的项目

D.发现没有合适的投标项目经理

Although writing from different points of view and with different techniques, writers in the Victorian Period shared one thing in common, that is, they were all concerned about ______.

A. the fate of the upper class

B. the reformation of the government
C. the fate of the common people

D. the future of their family class