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.

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.