Which of the following is an optional element in the PROC SORT syntax?

In PROC SORT, the OUT= option is indeed an optional element. The primary purpose of PROC SORT is to sort a dataset, and while specifying the dataset to sort (using the DATA statement) is mandatory, the OUT= option allows you to define a new output dataset that will contain the sorted data. If you do not specify an OUT= option, PROC SORT will overwrite the original dataset with the sorted data.

The DATA statement is essential as it indicates the dataset to be sorted. The BY statement is also necessary for determining the order of the sort, specifying one or more variables on which the sorting is based. The RUN statement, although it serves to execute the procedure in SAS, is generally not considered an optional part of the syntax, as it is used to indicate the end of the procedure step.

Understanding that the OUT= option is optional allows users the flexibility to either create a new sorted dataset or modify the existing one directly, depending on their analysis or data management needs.