The correct option is Network. The Network layer of the OSI Model is responsible for logical addressing and routing of data packets. It establishes paths for data to travel through the network based on logical addresses (like IP addresses) and determines the best route for data transmission. This layer also manages congestion control and error handling. The Application layer deals with user interfaces and application-level protocols, Presentation layer handles data formatting and encryption, and Transport layer ensures reliable data delivery.

Context Switch time is crucial in multitasking environments as it directly impacts system efficiency. It includes saving the state of the current process, loading the state of the next process, and updating necessary data structures.

The correct option is "UPDATE." The UPDATE statement is used to modify existing data in a database table. It allows you to change the values of one or more columns in one or more rows based on specified conditions.

Common pitfalls in dynamic programming include not recognizing overlapping subproblems, which leads to redundant computations; setting incorrect base cases, which can cause incorrect results; not optimizing space complexity, resulting in excessive memory usage; and not optimizing time complexity, leading to inefficient algorithms. Avoiding these pitfalls ensures efficient and correct dynamic programming solutions.

The main difference between TCP and UDP in the TCP/IP protocol suite is that TCP is connection-oriented and ensures reliable data delivery with error checking, while UDP is datagram-based and lacks built-in error checking and reliability mechanisms.

CRUD operations in RESTful APIs correspond to HTTP methods: GET for READ, POST for CREATE, PUT for UPDATE, and DELETE for DELETE. These methods provide a standardized way to interact with resources over the web.

Input validation and sanitization ensure that user input is validated and sanitized to prevent SQL injection attacks. Parameterized queries separate SQL code from user input, reducing the risk of SQL injection. Regularly updating and patching the web server and DBMS closes known vulnerabilities that attackers exploit. A WAF can detect and block SQL injection attacks, but it's not as effective as input validation and sanitization.

Normalization in a CRM system involves breaking down customer data into multiple tables such as contacts, orders, and products, linked by foreign keys. This reduces redundancy, ensures data consistency, and allows for efficient data retrieval and updates. Storing all customer data in one table would lead to redundancy and inefficiency, while separate databases or non-relational databases would not adhere to normalization principles.

The mutex (mutual exclusion) mechanism is employed to prevent multiple threads from simultaneously accessing shared resources, ensuring that only one thread can access the resource at a time, thus avoiding conflicts and data corruption.

WebSocket is suitable for real-time communication between the client and server because it establishes a persistent connection that allows bidirectional data flow with low latency. This eliminates the overhead of establishing new connections for each exchange, making it efficient for real-time applications such as chat, gaming, or collaborative editing. HTTP Long Polling involves repeated client-server requests, leading to higher latency and increased server load, making it less efficient for real-time scenarios. MQTT and XMPP are messaging protocols often used for IoT and instant messaging, respectively, but they are not optimized for real-time web applications like WebSocket.