Explanation:

Thrashing is a phenomenon that occurs in a computer system when it is excessively busy swapping data between physical memory and virtual memory. It is characterized by a high rate of page faults and a low CPU utilization. Thrashing can severely impact system performance and can lead to a significant decrease in overall system responsiveness.

Thrashing is caused by a combination of factors, including a high degree of multiprogramming and excessive page I/O. When the system is overloaded with too many processes or tasks, there may not be enough physical memory to hold all the required pages. As a result, the system constantly needs to perform page swaps between physical memory and the disk, resulting in excessive page I/O.

The excessive page I/O associated with thrashing leads to a decrease in system performance. The system spends a significant amount of time moving pages in and out of memory instead of executing actual instructions. This can lead to a decrease in CPU utilization, as the CPU is idle during the time it takes to perform page swaps.

In contrast to the other options listed, thrashing does not improve system performance. It is a detrimental condition that negatively impacts the overall performance and responsiveness of the system.

In summary, thrashing is a phenomenon that occurs when a computer system is excessively busy swapping data between physical memory and virtual memory. It is caused by a combination of factors, including a high degree of multiprogramming and excessive page I/O. Thrashing leads to a decrease in system performance and should be avoided to ensure optimal system operation.