Explanation:

✅ D. Use RowCount to ensure the rowset contains data
After retrieving a rowset using LookupRows, best practice is to check if any rows were actually returned before looping over them. This avoids runtime errors or empty loops. RowCount returns the number of rows in a rowset, so wrapping the loop in an IF RowCount(@rows) > 0 condition ensures the loop only executes when there’s data to iterate over.

❌ A. Use Row to return a specific row of the rowset
Row is used inside the FOR loop to access a specific row by index, like Row(@rows, @i). However, before even entering the loop, the developer should confirm whether there are any rows using RowCount. This makes option A a later step, not the immediate next step after retrieving the rowset.

❌ B. Set the rowset to a new array variable
There's no need to set the result of LookupRows to a new array variable. LookupRows already returns a rowset object. AMPscript does not support assigning this to an array type the way traditional programming languages might.

❌ C. Close the delimited AMPscrlpt Code Block
This is a syntax-related action, not a logical step related to looping or rowset handling. Proper closing of AMPscript blocks is always necessary, but this answer doesn’t address the functional logic needed before looping.