In which scenario would you use the ROLLUP operator for expression or columns within a GROUP BY clause?

In which scenario would you use the ROLLUP operator for expression or columns within a GROUP BY clause?

A.
to find the groups forming the subtotal in a row

B.
to create group-wise grand totals for the groups specified within a GROUP BY clause

C.
to create a grouping for expressions or columns specified within a GROUP BY clause in one direction, from right to left for calculating the subtotals

D.
to create a grouping for expressions or columns specified within a GROUP BY clause in all possible directions, which is cross-tabular report for calculating the subtotals