D . True. The TRUNC function, when applied to the difference between SYSDATE and hire_date divided by 7, will return the number of complete weeks of employment. The ORDER BY tenure DESC will sort the result in descending order, starting with the longest-serving employee.
A is incorrect because it does not include the DESC keyword necessary to start with the longest-serving employee. B is incorrect because ROUND could result in rounding up to the next week, which does not give the number of complete weeks. C is incorrect because the division is done by 17 instead of 7, which is likely a typo, and ROUND is used instead of TRUNC.