Which of the following best describes a passive scan?

a$.)$ The attacker analyzes the network and port scan results to determine which machines are the most vulnerable.

b$.)$ The attacker never comes in contact with the target network.

c$.)$ An additional scan to determine if the server is using a vulnerable version of some application or program.

d$.)$ The attacker gathers information about users and groups, banner information, and service account information to try and gain a foothold on the system.