A. Difference between a stationary and a nonstationary random process is: Stationary Process: A stationary process has constant statistical properties over time. These properties include mean, variance, and autocorrelation. In a stationary process, these properties do not change with time shifts. Non-stationary Process: A non-stationary process has statistical properties that vary over time. This variation can be in the mean, variance, or other moments of the distribution. Non-stationary processes often exhibit trends, seasonal patterns, or other systematic changes.