Which of the following is a true statement with regards to a NIDS?

Which of the following is a true statement with regards to a NIDS?

A.
A NIDS monitors and analyzes network traffic for possible intrusions.

B.
A NIDS is installed on the proxy server.

C.
A NIDS prevents certain types of traffic from entering a network.

D.
A NIDS is normally installed on the email server.