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.

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.

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.

The correct option is "Atomic." In the context of ACID properties, atomicity ensures that database transactions are either fully completed or not executed at all. This means that if a transaction fails or encounters an error, it will be rolled back to its initial state, maintaining data consistency. Atomicity is crucial for reliability and data integrity in database management systems.

Encapsulation is the process of bundling data (attributes) and functions (methods) that operate on the data into a single unit called a class. It helps in hiding the internal state of an object and only exposing the necessary functionality to the outside world. This enhances security, modularity, and reusability in object-oriented programming.

A VLAN Router (also called a Layer 3 switch or router) is used to facilitate communication between different VLANs. It operates at Layer 3 of the OSI model, routing traffic between VLANs based on IP addresses. This enables segregation of network traffic for security or organizational purposes while allowing controlled communication between VLANs as needed.

Mutation testing involves deliberately introducing small changes (mutations) to the source code and then running the test suite to check if the tests detect these mutations. This technique helps evaluate the effectiveness of the test cases by measuring their ability to detect changes in the code, thereby improving the quality and reliability of the test suite. It is significant as it helps in identifying weak spots in the test suite and improving overall test coverage.

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).

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.

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.