finite cell line (有限细胞系)
参考答案：
在体外的生存期有限即不能长期传代的细胞系。
What did he do
A．He telephoned me.
B．He picked up the phone.
C．He put the receiver down.
D．He put my hanger up.
案卷密级有（）。
A.绝密年
B.永久
C.机密
D.短期
E.秘密
