Designing a thread management system for a web server application involves strategies for high performance and scalability. Using a thread pool allows for the reuse of threads, reducing the overhead of thread creation and destruction for each request and improving overall performance. Implementing asynchronous I/O operations helps in avoiding thread blocking, enabling the server to handle more concurrent requests efficiently. Load balancing across multiple servers distributes incoming requests evenly, enhancing scalability by utilizing resources effectively. Mutex locks are essential for ensuring thread-safe access to shared resources but may not directly contribute to performance and scalability in the context of handling concurrent requests in a web server application.

The correct option is Waterfall. The Waterfall model follows a sequential approach, progressing through phases like Requirements, Design, etc.

Log-structured file systems provide faster write operations and improved crash recovery through sequential writes and transaction logging. However, they may have higher storage overhead and longer read times due to data fragmentation. Their advantages include better data integrity and reduced risk of data loss, but they may lack compatibility with legacy systems.

Cross-site scripting (XSS) is a type of security vulnerability where attackers inject malicious scripts into web pages viewed by other users. These scripts can execute unauthorized actions on the user's behalf, such as stealing session cookies or performing actions on the user's behalf without their consent. This type of attack targets client-side scripts in web applications, making it crucial for developers to validate and sanitize input to prevent XSS attacks.

The purpose of a sprint retrospective in Agile is to identify areas for improvement within the team's processes, communication, and collaboration. It allows team members to reflect on what went well, what could be improved, and how to implement those improvements in the next sprint. This continuous feedback loop fosters a culture of learning and adaptation in Agile projects.

The correct option is Presentation. The Presentation layer of the OSI Model deals with the presentation and encryption of data. It is responsible for data translation, encryption, and decryption to ensure that data sent from one system can be properly understood by another system. This layer also handles data compression and decompression. The Data Link layer manages error detection and correction, the Application layer deals with user applications, and the Transport layer ensures end-to-end communication.

The X-XSS-Protection header is used to mitigate Cross-Site Scripting (XSS) attacks in web applications. XSS attacks involve injecting malicious scripts into web pages, which can then execute in users' browsers, leading to data theft, session hijacking, and other security compromises. The X-XSS-Protection header instructs browsers to activate their built-in XSS protection mechanisms, such as filtering or blocking potentially dangerous scripts, thereby reducing the risk of successful XSS attacks. Implementing this header is an important security measure to safeguard against XSS vulnerabilities and protect users' sensitive information.

The pop operation removes the last node from a linked list, updating pointers accordingly to disconnect it from the list and deallocate its memory if necessary.

Unit testing is focused on verifying the functionality of individual units or modules of code. It is performed early in the development process to detect and fix bugs at a granular level, ensuring that each unit of code functions as intended. This helps in improving code quality, identifying issues early, and facilitating easier integration with other components.

When implementing a guest Wi-Fi network for a hotel, ensuring security for both guests and the hotel's internal network involves implementing guest isolation to prevent guests from accessing internal resources. Captive portals with authentication ensure only authorized users gain access. MAC address filtering adds an additional layer of security by allowing only specific devices to connect. Configuring firewall rules restricts unauthorized access and protects sensitive data. These measures collectively enhance security while providing convenient guest access.

The correct option is "Hypervisor." A hypervisor, also known as a virtual machine monitor (VMM), allows multiple virtual machines (VMs) to run on a single physical machine by abstracting and managing the underlying hardware resources. It provides isolation, resource allocation, and control over the VMs, enabling different operating systems to coexist on the same hardware.

Data integrity in a relational database can be ensured using SQL constraints such as PRIMARY KEY (to enforce uniqueness), FOREIGN KEY (to maintain referential integrity), CHECK (to validate data), and UNIQUE (to enforce uniqueness).