What happens if you use KEEP= or DROP= in a DATA step line?

When you use KEEP= or DROP= in a DATA step, you are specifying which variables to retain or exclude in the resulting dataset. Option C is correct because these statements directly manipulate the set of variables that are included in the final output dataset, allowing you to selectively include or exclude specified variables.

The behavior of KEEP= and DROP= is such that if you drop a variable, it will not be present in the resulting dataset, and hence you won’t be able to reference it afterward in the DATA or subsequent steps. However, you can still reference dropped variables within the DATA step itself as long as they are included in the input dataset. The inclusion of KEEP= and DROP= enhances the flexibility in managing variables and helps optimize data processing by reducing the size of the datasets when unnecessary variables are excluded from the final output.

The other options do not correctly reflect how KEEP= and DROP= function. The immediate removal implied in the first choice does not take into account that while the variables may not appear in the output dataset, their references can still exist in the DATA step until the end of processing. The second option inaccurately suggests these statements impose restrictions on variable types, which they do not. Lastly, stating that KEEP= and DROP= must be