Last term before I got the message that two of my classmates will not attend our final discussion, I cried. Undoubtedly, I am an extreme anxious person.I feel nervous if anything on my schedule will not carried out.My personality has always bothered me a lot. One thing I would like to changing is my character.I attended the lecture a few week ago. The lecturer said a sentence that left an impression on me. “I feel strongly which I can make it.”From then on, I have regarded it for my motto. I encourage myself to become a positive person who will not to be beaten by any difficulties

SAN上的文件和目录是由（）来管理的。

A.网络操作系统

B.数据库系统

C.存储操作系统

D.服务操作系统