Using WebSocket allows real-time communication between clients and the server, making it ideal for notifying users when someone is typing. setTimeout and clearTimeout are more suitable for handling delays and timeouts, not real-time updates. AJAX polling introduces unnecessary overhead and delays. The oninput event listener is used for detecting input changes, not real-time status updates.

Merge sort is a classic example of a divide and conquer algorithm, where the sorting process involves dividing the array into smaller subarrays, sorting them individually, and then merging them back together in sorted order.

Scrum is an Agile methodology that emphasizes adaptability and customer collaboration over strict planning. It encourages iterative development, frequent feedback, and a focus on delivering value to customers. Scrum teams are self-organizing and cross-functional, with a Scrum Master facilitating the process rather than dictating tasks. This approach promotes flexibility, continuous improvement, and customer satisfaction by responding to changing requirements throughout the development cycle.

Node.js clustering allows applications to utilize multiple CPU cores efficiently by creating child processes (workers) using the cluster module. Each child process runs on a separate core, enabling parallel processing and improved performance. This approach is particularly effective for scaling applications across multiple cores without relying solely on the single-threaded nature of Node.js.

The Repository pattern is commonly used in RESTful APIs to abstract the data access layer and provide a simplified interface for accessing related resources. It helps in organizing code and separating concerns by providing a centralized mechanism for handling database operations related to specific resources.

In a legacy system, normalization involves identifying redundant data and dividing tables to eliminate anomalies such as update, insertion, and deletion anomalies. This is achieved by breaking down data into fewer tables, using foreign keys to establish relationships, and ensuring data integrity. Combining tables or using non-normalized data would not address the underlying issues of redundancy and anomalies.

The block size in a file system plays a crucial role in determining the speed of file access. A smaller block size can lead to more efficient storage utilization for small files but may result in increased overhead for large files due to more blocks being allocated. On the other hand, a larger block size can improve the performance of accessing large files but may lead to wasted space for small files. Therefore, the block size choice depends on the expected file sizes and access patterns in a given system, balancing efficiency and performance accordingly.

The ACID property that ensures transactions are isolated from each other to prevent interference is Isolation. Isolation ensures that concurrent transactions do not see each other's intermediate states, thus preventing interference and maintaining data integrity.

The correct option is "Replication." Durability in ACID properties refers to the guarantee that once a transaction is committed, its changes will persist even in the event of system failures or crashes. Replication techniques, such as maintaining multiple copies of data across different storage locations or using backup servers, are employed to ensure data durability. These strategies help in recovering data and maintaining system availability despite hardware or software failures.

Representational State Transfer (REST) is an architectural style for distributed hypermedia systems. It emphasizes scalability, reliability, and the uniform interface between components. RESTful APIs use HTTP methods like GET, POST, PUT, DELETE to manipulate resources.