Link aggregation is a technique that combines multiple physical network links into one logical link with higher bandwidth and redundancy. It can take advantage of all the available bandwidth of the NICs (Network Interface Cards) on the server and provide load balancing and failover capabilities for network traffic. Verified References: [Link aggregation], [NIC]

Drives, fans, and power supplies are server components that can most commonly be replaced without downtime if they are hot-swappable. Hot-swappable components can be removed and inserted while the server is running, without affecting its operation or performance. Drives store data and applications, fans cool down the server components, and power supplies provide electricity to the server. Replacing these components can prevent data loss, overheating, or power failure. References: CompTIA Server+ Certification Exam Objectives, Domain 2.0: Hardware, Objective 2.2: Given a scenario, install, configure and maintain server components.

The live failover testing method is the most likely one that the server administrator is performing when creating a downtime scenario and taking the necessary steps. A live failover test involves switching from the primary system to the secondary system (or backup site) in a real environment, without any simulation or preparation. A live failover test can evaluate the effectiveness and readiness of the disaster recovery plan, but it also carries a high risk of data loss, corruption, or disruption. Reference:
https://www.ibm.com/cloud/learn/disaster-recovery-testing

A subscription license is a type of license that grants the user the right to use a product or service for a fixed period of time, usually a year. The user pays a recurring fee, regardless of how much they use the product or service. Subscription licenses are common for cloud-based software and services, such as Microsoft 3651 or DocuSign2.
References = 1: Compare All Microsoft 365 Plans (Formerly Office 365) - Microsoft Store(https://www.microsoft.com/en-us/microsoft-365/buy/compare-all-microsoft-365-products) 2: DocuSign Pricing | eSignature Plans for Personal & Business(https://ecom.docusign.com/plans-and-pricing/esignature)

Round robin is an example of load balancing. Load balancing is the method of distributing network traffic equally across a pool of resources that support an application. Load balancing improves application availability, scalability, security, and performance by preventing any single resource from being overloaded or unavailable. Round robin is a simple load balancing algorithm that assigns each incoming request to the next available resource in a circular order. For example, if there are three servers (A, B, C) in a load balancer pool, round robin will send the first request to server A, the second request to server B, the third request to server C, the fourth request to server A again, and so on.
Reference: https://simplicable.com/new/load-balancing