Explanation
RJ11 is a type of connector that is commonly used for analog phone lines. RJ11 has four wires and six positions, but only two or four of them are used. A technician can crimp an RJ11 connector to a new phone line to install an analog desk phone for a new receptionist. References:
https://www.comptia.org/blog/what-is-rj11

Explanation
A core switch is the most likely device causing the issue where users on each floor have stable connectivity, but do not have connectivity to other floors. A core switch is a high-performance switch that connects multiple access switches in a network. An access switch is a switch that connects end devices, such as computers and printers, to the network. A core switch acts as the backbone of the network, providing interconnection and routing between different subnets or VLANs. If the core switch is malfunctioning or misconfigured, it can prevent communication between different segments of the network, resulting in intermittent connectivity issues. References: [CompTIA Network+ Certification Exam Objectives], Core Switch vs Access Switch:
What Are the Differences?

Explanation
A reservation should be configured to ensure a device with a specific MAC address is always assigned the same IP address from DHCP. A reservation is a feature of DHCP that allows an administrator to assign a fixed IP address to a device based on its MAC address. This way, the device will always receive the same IP address from the DHCP server, even if it is powered off or disconnected from the network for a long time. References:
https://docs.microsoft.com/en-us/windows-server/troubleshoot/configure-dhcp-reservations

Explanation
Active-active refers to more than one NIC being active at the same time. In my opinion, this question is referring to a recovery site (hot, warm, cold, cloud)

Explanation
Hub-and-spoke is a network topology where each node connects to a central switching device, such as a hub or a switch. All traffic between the nodes must pass through the central device, which acts as a single point of communication and control. Hub-and-spoke topology is simple, easy to manage, and cost-effective, but it also has drawbacks, such as low redundancy, high latency, and scalability issues.
References:
Network Topologies - N10-008 CompTIA Network+ : 1.21
CompTIA Network+ Certification Exam Objectives, page 92