SSID stands for Service Set Identifier. It is a unique name that identifies a specific wireless network. Devices use SSIDs to connect to the correct network among the multiple networks available in the vicinity.

The Network Layer (Layer 3) of the OSI Model is responsible for routing and forwarding packets. This layer handles logical addressing, routing, and traffic management within a network. It ensures that data packets are properly routed from the source to the destination across different networks, making decisions based on logical addressing information (such as IP addresses). Option 1 is correct because the Network Layer specifically deals with routing functions in the OSI Model.

The purpose of the Singleton design pattern is to ensure that a class has only one instance and provide a global point of access to it. This is particularly useful in scenarios where you want to control access to resources or manage shared resources efficiently. The pattern also helps in maintaining a single instance throughout the application's lifecycle, preventing unnecessary duplication and ensuring consistency in data and behavior.

Firewalls play a crucial role in web application security by filtering network traffic to identify and block malicious or unauthorized requests. They act as a barrier between the internet and the web server, inspecting incoming and outgoing data packets based on predefined rulesets. By analyzing factors such as IP addresses, port numbers, and packet contents, firewalls can detect and thwart various cyber threats, including DDoS attacks, SQL injection attempts, and unauthorized access attempts. This proactive defense mechanism helps prevent malicious entities from compromising the web application's integrity, ensuring continuous availability and data confidentiality for users.

The correct option is 'Top.' To implement a stack using arrays, we use a 'Top' pointer to keep track of the topmost element in the stack, allowing us to perform push and pop operations efficiently.

The correct option is "AVG()." The AVG() function in SQL is used to calculate the average value of a numeric column in a table. It excludes NULL values while calculating the average.

Paging is a memory management scheme where physical memory is divided into fixed-sized blocks called frames, and logical memory is divided into fixed-sized blocks called pages. Each process is then assigned contiguous blocks of frames for its pages. Paging helps in efficient memory utilization and reduces external fragmentation.

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.

A race condition occurs in concurrent systems when the outcome of operations depends on the timing or interleaving of multiple threads. It leads to data inconsistency and unpredictable results. Synchronization mechanisms like mutexes and semaphores are used to prevent race conditions by ensuring that only one thread can access a shared resource at a time, thereby maintaining data integrity and thread safety.