During an examination of a time-and-attendance system, an internal auditor determined that control over the time card system was excellent, all employees recorded their vacation time on weekly time cards, and each time card was properly reviewed and signed by a plant supervisor. The auditor also discovered one worker with no vacation time recorded on any time card for the period audited. Which of the following is reasonable for the auditor to conclude?

A. There was an error in the time cards for the one employee.
B. There were errors in the time cards for other employees.
C. Organizational policy required plant workers to take vacation time each year.
D. The one employee took no time off for vacation during the period audited.