Which of the following is false about BY-group processing?When you use the BY statement with the SET statement, A. FIRST. and LAST. are stored in the data set. B. FIRST. and LAST. identify the first and last observation in each BY group, in that order.C. the DATA step automatically creates two variables, FIRST. and LAST. for each variable in the BY statement.D. the data sets that are listed in the SET statement must be indexed or sorted by the values of the BY variable(s).