A doubly linked list is one in which each node has two pointers, one pointing to the next node and one pointing to the previous node, forming a bidirectional sequence.

Relational databases handle transactions by logging changes made during transactions, allowing for rollbacks in case of failure. This logging mechanism ensures data consistency by providing a point-in-time view of the database and enables recovery to a consistent state. Backup strategies, encryption, and access control are important for data protection but not directly related to transaction handling and data consistency in relational databases.

The Network Layer, which is Layer 3 in the OSI model, is responsible for routing packets between different networks. It handles logical addressing, routing, and traffic control functions. Routers operate at this layer, using IP addresses to forward packets across networks based on routing tables and algorithms.

React provides multiple ways to manage state in components, such as using component state, Redux for global state management, Context API for sharing state, and passing data via props.

Option 2 explains how to effectively use abstraction to create a superclass with common properties and methods for vehicles, ensuring a clear and structured representation of different vehicle types in the software system. This approach promotes code reusability and scalability by allowing specific vehicle classes to inherit from the common superclass while maintaining distinct functionalities. Abstraction also helps in managing complexity by focusing on essential attributes and behaviors at a higher level.

Inheritance in Object-Oriented Programming (OOP) allows a class to extend properties and behaviors of another class. When a class inherits from another class, it gains access to its attributes and methods, allowing for code reuse and the creation of hierarchical relationships. This helps in building more complex and structured programs by organizing classes based on their common characteristics and functionalities.

Versioning in RESTful APIs involves managing different versions of the API to accommodate changes while ensuring backward compatibility and not breaking existing client implementations. It allows API providers to introduce new features, update functionality, or fix issues without disrupting existing client applications. This is crucial for maintaining a stable and predictable API ecosystem, where clients can rely on consistent behavior despite changes in the underlying API implementation. Versioning also helps improve API documentation by clearly delineating changes between versions, aiding developers in understanding API updates and making informed decisions. While versioning indirectly impacts security and database optimization by enabling controlled changes, its primary focus is on maintaining API compatibility and developer experience.

CSS preprocessors like Sass, Less, and Stylus are tools that extend the capabilities of CSS by adding features like variables, mixins, nesting, and functions. They enhance the development process by making CSS code more organized, reusable, and maintainable. Preprocessors also streamline workflows and improve code efficiency, leading to faster development and easier maintenance of stylesheets.

The data structure that most closely resembles the behavior of a stack is a queue. While a stack follows the Last In, First Out (LIFO) principle, where the last element added is the first one to be removed, a queue follows the First In, First Out (FIFO) principle, where the first element added is the first one to be removed. Queues are often used in scenarios such as managing processes in operating systems, implementing printer spooling, and handling requests in network communication.

FTP (File Transfer Protocol) and SFTP (Secure File Transfer Protocol) differ significantly in terms of security. FTP transmits data in plain text, making it vulnerable to interception and unauthorized access. In contrast, SFTP encrypts data during transmission, enhancing security by protecting sensitive information from being compromised.