The correct ORDER BY clause needed to generate the displayed output is the one that orders based on the commission (comm) in descending order while placing nulls last, followed by ordering based on the employee name (ename) to ensure a secondary order. The ordering shown in the output indicates that the rows are sorted first by the comm values in descending order with non-null values appearing first, and then alphabetically by ename. Therefore, the correct clause is 'ORDER BY comm DESC NULLS LAST, ename'.