某研究小组为测定药物对体外培养细胞的毒性,准备对某种动物的肝肿瘤细胞(甲)和正常肝细胞(乙)进行动物细胞培养.下列叙述正确的是( )
A:制备肝细胞悬液时,可用胃蛋白酶处理肝组织块
B:恒温培养箱中的CO2浓度维持在5%左右,以促进细胞呼吸
C:为了保证细胞培养所需的无毒环境,需大量添加各种抗生素
D:本实验应设置对照实验,以检测药物对甲、乙的毒性大小
在“一国两制”中,国家的主体是( )
American boys and girls like watching TV. Some children spend six hours a day at school and four to six hours a day in front of the TV sets. Some children even watch TV for eight hours or more on Saturday. Television(电视)is like books and films . A child can learn good things and bad things from it. Some TV programs help children to understand the news, the people and places from other countries. With TV, children do not have to go out to see films, they can hear interesting music or watch a game at home. But some programs are bad for children, so parents sometimes help them to find other interesting and useful things to do.
下列成语中,完全没有错误的一项是( )。
人体最大的消化腺是( )
已知:
2Fe2++Br2═2Fe3++2Br﹣
2Fe3++2I﹣═2Fe2++I2