Without proper safeguards, every part of a network is vulnerable to a security breach or u

Without proper safeguards, every part of a network is vulnerable to a security breach or unauthorized activity from （）, competitors, or even employees. Many of the organizations that manage their own （） network security and use the Internet for more than just sending/receiving e-mails experience a network （）— and more than half of these companies do not even know they were attacked. Smaller （） are often complacent, having gained a false sense of security. They usually react to the last virus or the most recent defacing of their website. But they are trapped in a situation where they do not have the necessary time and（）to spend on security.

A.intruders

B.terminals

C.hosts

D.users@@@SXB@@@A.exterior

B.internal

C.centre

D.middle@@@SXB@@@A.attack

B.collapse

C.breakdown

D.virus@@@SXB@@@A.users

B.campuses

C.Companies

D.networks@@@SXB@@@A.safeguards

B.businesses

C.experiences

D.Resources

请帮忙给出正确答案和分析，谢谢！