To display the trend in the number of dogs housed by the SPCA over 20 years, which type of plot is most appropriate?

A timeplot is the most appropriate choice for displaying the trend in the number of dogs housed by the SPCA over 20 years because it is specifically designed to show how a variable changes over time. In a timeplot, the x-axis represents time, while the y-axis represents the variable being measured, in this case, the number of dogs. This visualization allows for easy identification of trends, patterns, and fluctuations in the data across the specified period.

Other types of plots serve different purposes. A bar chart is typically used for categorical data to compare the sizes of different groups rather than to show changes over time. A histogram is meant for displaying the distribution of numerical data across different intervals, not for examining trends over time. Meanwhile, a boxplot focuses on summarizing the distribution of a dataset and highlighting outliers rather than showing changes through time. Thus, the timeplot effectively communicates the developmental narrative of the data, making it the ideal choice for this scenario.