Which of the following best describes a Circuit Level Gateway?

Question $72$ options:

Network$-$based device that modulates carrier waves to encode digital data for transmission then demodulates the signals to decode the transmitted information

Maintains state information from one packet to another in the input stream to determine threats and grant access according to information from multiple packets.

Operates at the Session Layer $($Layer $5)$ to monitor the TCP handshake between packets to determine if the session is legitimate.

Prevents access to and transmission of protected files based upon predefined rule sets