规定采油速度和（）是油田开发原则中的重要内容。

A、开采方式

B、开发层系

C、布井原则

D、稳产期限

Changing rescuers while carrying out artificial respiration should be done（）.

A.without losing the rhythm of respiration

B.only with the help of two other people

C.by not stopping the respiration for more than 5 minutes

D.at ten-minute intervals