---_________?

---With pleasure. What is it?

A．May I ask a favor of you

B．Can I do something for you

C．How do you find it

D．Are you satisfied with a job

液氮保存和复苏细胞的基本原则是

A．快冻快溶

B．慢冻慢溶

C．慢冻快溶

D．快冻慢溶

E．不必加冷冻保护剂