RFID stands for Radio Frequency Identification, and it is a technology that uses electromagnetic fields to identify and track objects that have RFID tags attached to them. RFID tags are small devices that store information and can be read by RFID readers. RFID is most likely used to control door access because it allows for contactless and convenient authentication of authorized personnel. For example, an employee can use an RFID card or key fob to unlock a door by holding it near an RFID reader installed on the door. The reader will scan the tag and verify its ID number with the access control system, which will grant or deny access based on the predefined rules and permissions. RFID is a common and widely used type of door access control system, as it offers security, efficiency, and flexibility.

Explanation
A damaged battery can cause a laptop to overheat and swell, making it unable to sit level on the workspace. A swollen battery can also pose a fire hazard and damage other components of the laptop, such as the motherboard or keyboard. The technician should replace the battery as soon as possible and dispose of it properly according to local regulations. Reference:
https://partners.comptia.org/docs/default-source/resources/a-core-series-combined-content-guide (page 25)

The correct answer is C. Ethernet.
An Ethernet cable is a type of network cable that is used to connect devices on a local area network (LAN), such as computers, routers, switches, and modems. Ethernet cables have RJ-45 connectors at both ends, which are similar to telephone jacks but larger. Ethernet cables can carry data signals at speeds ranging from 10 Mbps to 10 Gbps, depending on the type and quality of the cable.
A cable modem is a device that connects to a coaxial cable from a cable service provider and provides high-speed internet access. A SOHO router is a small office/home office router that connects to a cable modem or DSL modem and provides network and internet access to multiple devices on a LAN. A SOHO router typically has one WAN port and four LAN ports. The WAN port is used to connect to the cable modem or DSL modem, while the LAN ports are used to connect to computers or other devices on the LAN.
To connect a cable modem to a SOHO router, an Ethernet cable is needed. The Ethernet cable is plugged into the WAN port of the SOHO router and the Ethernet port of the cable modem. This allows the SOHO router to receive an IP address from the cable service provider and share it with the devices on the LAN using network address translation (NAT). The SOHO router also provides firewall and wireless features for the LAN.
The other options are incorrect because they are not suitable for connecting a cable modem to a SOHO router. FireWire is a type of serial bus that is used to connect devices such as digital cameras, external hard drives, and audio interfaces. FireWire cables have different connectors than Ethernet cables and cannot be used for network communication. Fiber is a type of optical cable that uses light signals to transmit data over long distances. Fiber cables have special connectors that are not compatible with Ethernet ports. Coaxial is a type of copper cable that has a central conductor surrounded by an insulating layer and a braided shield. Coaxial cables are used for cable TV and internet services, but they cannot be directly connected to Ethernet ports without an adapter.
Reference:
CompTIA A+ Certification Exam: Core 1 Objectives (220-1001)
Installing and Configuring a Cable Modem/DSL Router
Cisco 831 Router and SOHO 91 Router Cabling and Setup Quick Start Guide