To get 500 hosts you need 9 host bits, thats gives us an mask of 255.255.254.0 /23. This gives us 510 hosts, with 508 useable addresses. They did not mention expandability, so we should not read that into the answer, they did however, asked to have the fewest unused addresses.

Biometrics is a type of authentication that uses a person's physical characteristics, such as fingerprints, iris, or face, to verify their identity. An access control vestibule is a small room or area that separates two spaces and allows only one person to enter or exit at a time. Biometrics in an access control vestibule is the most effective physical security method to prevent tailgating, which is the unauthorized entry of a person behind another person who has legitimate access.
References: Network+ Study Guide Objective 5.1: Summarize the importance of physical security controls.

Coaxial cable is a type of cable that consists of a central copper conductor surrounded by an insulating layer and a braided metal shield. Coaxial cable is commonly used to connect a cable modem to an ISP by transmitting data over cable television networks. Coaxial cable can support high bandwidth and long distances with minimal interference or attenuation. References:
https://partners.comptia.org/docs/default-source/resources/comptia-network-n10-008-exam-objectives-(2-0),
https://www.techopedia.com/definition/4027/coaxial-cable