Priority Scheduling ensures fairness by assigning priorities to processes based on criteria such as importance or resource requirements. This ensures that critical tasks get appropriate CPU time, promoting fairness.

Multi-factor authentication (MFA) adds an extra layer of security by requiring users to provide multiple forms of identification before accessing sensitive data. This can prevent unauthorized access even if login credentials are compromised. Strict access control policies limit access based on roles and responsibilities, reducing the risk of unauthorized access. Security awareness training educates employees about potential threats and best practices, but it alone may not prevent unauthorized access. Encryption protects data from being accessed by unauthorized parties, but it doesn't prevent access attempts.

The correct option is Single Responsibility Principle. This principle suggests that a class should have only one job or reason to change, leading to more modular, maintainable, and understandable code.

In Agile methodologies, estimating the effort required for each user story or task is commonly referred to as "Story Pointing." Story Pointing involves assigning relative values (such as story points) to different tasks or user stories, based on their complexity, risk, and effort required. This practice helps Agile teams plan and prioritize their work effectively during sprint planning sessions. Sprint planning involves determining which user stories and tasks will be tackled in the upcoming sprint, whereas backlog refinement is the ongoing process of reviewing and updating the product backlog. Velocity tracking, on the other hand, is a measure of how much work a team can complete in a sprint, often calculated based on past performance. Therefore, the most appropriate option for estimating effort in Agile is Story Pointing.

Middleware functions in Express.js have access to the request and response objects, as well as the 'next' function which is used to pass control to the next middleware function in the stack.

The OSI Model, or Open Systems Interconnection Model, is used to provide a conceptual framework that standardizes the functions of a networking or telecommunication system into seven layers. It helps in understanding and designing complex network architectures by dividing the communication process into manageable layers, each responsible for specific tasks. Option 2 is correct because the OSI Model indeed provides a structured framework for various networking devices to communicate effectively.

Middleware in Express.js executes additional functions between receiving a request and sending a response. It can perform tasks like authentication, logging, parsing data, and modifying the request/response objects. Middleware functions have access to the request object (req), response object (res), and the next middleware function in the applications request-response cycle. This flexibility allows developers to modularize and enhance the functionality of their Express.js applications.

The "C" in ACID stands for Consistency. This property ensures that all database transactions must follow rules and constraints defined in the database schema, maintaining data validity and integrity before and after each transaction.

Heap Sort is the ideal choice for implementing a priority queue. It has a time complexity of O(n log n), making it efficient for maintaining a priority queue structure. Selection Sort, Bubble Sort, and Merge Sort have higher time complexities and are less suitable for priority queue operations.

Option 1 outlines the initial steps of a post-mortem analysis, including forensic analysis, root cause identification, and impact assessment, which are crucial for understanding the breach. Option 2 mentions additional security measures but focuses more on prevention rather than post-incident analysis. Option 3 includes general security measures but lacks specific actions for analyzing the breach. Option 4 involves law enforcement collaboration and incident response, which are important but come after the initial analysis phase.