That's very kind  ______  you. I know it's very hard  _______  you to do that.

A．of, of

B．of, for

C．for, of

D．for, for

关于离心式压缩机启动前的准备工作，下列选项正确的是（）

A、根据工艺情况调整并最终关闭防喘振阀

B、投用隔离氮和二级缓冲气，再启动润滑油泵

C、先启动润滑油泵，干气密封系统待冲转前投用

D、确认出、入口阀门关闭，待低速暖机后打开