Choice "C" is correct. The approval of a summary of hours for each employee is performed by the department supervisor as the department supervisor observes whether the amount of each employee's reported hours is correct and whether the employee is being compensated for time actually worked.
Choice "a" is incorrect. The departmental supervisor approves payroll. If the departmental supervisor distributed paychecks directly to departmental employees, then this would be incompatible functions - the departmental supervisor would have access to assets (distributing paychecks) and also authorization of the transaction (approval of payroll). The departmental supervisor could dismiss an employee and not notify human resources, keep the dismissed employee's paycheck, and forge an endorsement on the employee's check.
Choice "b" is incorrect. The pay rate is established by the human resource department. If the departmental supervisor set the pay rates, then he/she could be in collusion with the employee and obtain a kickback for paying an employee more than an established rate for a certain pay grade.
Choice "d" is incorrect. Hiring employees and authorizing them to be added to the payroll is performed by the human resources department. If the departmental supervisor could hire employees, then he/she could hire someone not qualified for the position and be in collusion with the employee and obtain a kickback from the employee. A fictitious employee could also be "hired."