The setTimeout() function in JavaScript executes a function once after a specified delay, while setInterval() executes a function repeatedly at a specified interval until stopped. Understanding these differences is key to managing timing in JavaScript applications.

The correct option is Requirement Analysis. This phase is crucial as it involves gathering and documenting the software requirements from stakeholders, including end-users, clients, and business analysts. It sets the foundation for the entire software development process by defining what the system should do and how it should behave. During this phase, stakeholders' needs and expectations are analyzed, and feasibility studies may also be conducted to assess the project's viability.

Containerization is lightweight as containers share the host OS kernel, reducing resource overhead compared to traditional virtualization, which requires separate OS instances for each virtual machine, leading to higher resource utilization.

Option 2 provides essential measures for securing user authentication, including HTTPS for data encryption, strong password hashing, and session management practices. Multi-factor authentication (MFA) adds an extra layer of security but is not explicitly mentioned in Option 2. OAuth and OpenID Connect are more related to third-party authentication methods, not the core design of a secure authentication system.

Option 3 provides a key strategy for ensuring efficient routing and switching in a large enterprise network by implementing redundant links. This helps in load balancing, minimizing downtime, and ensuring redundancy, which are crucial for handling high traffic volume and maintaining network reliability. Using VLANs (Option 1) is important for network segmentation but may not directly address redundancy and high traffic volume concerns. Dynamic routing protocols (Option 2) aid in efficient route selection but may not specifically focus on redundancy. Quality of Service (Option 4) is crucial for traffic prioritization but does not directly address routing and redundancy concerns.

The correct option is "Facade." The Facade design pattern is utilized to provide a simplified interface to a larger body of code, such as a subsystem or a complex set of classes. It acts as a unified interface that hides the complexities of the subsystem and provides a simpler way for clients to interact with it. This pattern promotes loose coupling between subsystems and clients, enhancing the maintainability and scalability of the codebase.

The correct option is "Network." In the TCP/IP model, the Network layer is responsible for logical addressing. This includes assigning IP addresses and routing packets between different networks. The Transport layer (Option 2) is responsible for end-to-end communication and includes protocols like TCP and UDP. The Data Link layer (Option 3) deals with the physical connection between devices and includes protocols like Ethernet. The Application layer (Option 4) is responsible for providing user interfaces and services.

The purpose of query optimization in database management systems is to improve query performance. This involves identifying and selecting the most efficient execution plan for a given query, considering factors such as index usage, join methods, and data access paths. Query optimization aims to minimize resource utilization and response time for queries, enhancing overall system performance.

An index primarily enhances the efficiency of retrieval operations in a database. When a query needs to fetch specific data from a large dataset, indexes allow the database system to locate the required rows or entries more quickly, reducing the time it takes to retrieve data. This is particularly crucial in scenarios where databases deal with massive amounts of data and need to retrieve specific information efficiently.

Stable sorting algorithms maintain the relative order of equal elements in the sorted output as they were in the original input. Merge Sort is an example of a stable sorting algorithm because it preserves the order of equal elements during the merge phase. Quick Sort, Heap Sort, and Bubble Sort are not inherently stable unless additional steps are taken to maintain stability, such as using indexes or comparing indices during sorting. Understanding stable sorting is crucial in scenarios where maintaining the original order of equal elements is necessary.