Which of the following show residuals divided by their standard deviations?

The correct answer is D. all of the mentioned.

• rstudent is the studentized residual, which is the residual divided by its standard error.
• cooks.distance is a measure of how much a data point influences the fit of the model. It is calculated as the sum of the squared standardized residuals for that data point.
• rstandard is the standardized residual, which is the residual divided by its standard deviation.

All of these measures are used to identify outliers and influential data points. Outliers are data points that are far away from the rest of the data, and influential data points are data points that have a large impact on the fit of the model.