Thrashing occurs when a system has insufficient physical memory, causing excessive paging as the operating system continuously swaps data between RAM and disk. This leads to high overhead and severely degrades system performance, as more time is spent on paging rather than executing processes.

Modern operating systems use preemptive multitasking to enhance user interactivity and system responsiveness. It allows the operating system to interrupt a running process and switch the CPU to another process, ensuring that all processes receive appropriate attention and that the system remains responsive to user inputs.

Paging is a memory management scheme that allows the physical address space of a process to be non-contiguous. It eliminates the need for contiguous allocation of physical memory and thus reduces fragmentation by dividing memory into fixed-sized pages.

The critical section problem can be resolved using synchronization mechanisms such as semaphores. Semaphores are variables used to control access to common resources by multiple processes in a concurrent system, ensuring that only one process can enter the critical section at a time.

Round-robin scheduling is a time-sharing scheduling algorithm used by the operating system to handle the execution of multiple processes. Each process is assigned a fixed time slot (quantum), and processes are cycled through in a circular order, ensuring that all processes get a fair share of CPU time.

The Page Table is typically stored in the main memory (RAM). It is used by the operating system to keep track of the mapping between virtual addresses and physical addresses, facilitating virtual memory management.

Deadlock occurs when two or more processes are unable to proceed because each is waiting for a resource held by the other. This situation results in a standstill where none of the processes can continue execution.

A context switch occurs when the operating system saves the state of the currently running process and loads the state of another process. This allows the CPU to switch between processes efficiently, enabling multitasking and better utilization of system resources.