WHO培训遗留问题（1）

Wilden

之前参加了一个WHO老师的培训，看到有三个问题，英文较差，可能存在理解的歧义，各位大拿分析下？
1.What is the difference between a Grade B and a Grade A operator ?
文件资料参考原文为can not be in grade A until fully qulified-assistant in grade B

2.Under what circumstances could a Grade A operator be “dis-qualified” ?

3.Once an aseptic operator passes a media fill they should not have to repeat the interventions program.
意思是一旦无菌操作人员已然干预过培养基无菌灌封（被动），就没必要进行主动干预的意思么？