Choice "C" is correct. Access control software is a preventive control. It prevents "bad people" from accessing an organization's systems and data.
Choice "d" is incorrect. Contingency planning would be considered a corrective control.
Choice "b" is incorrect. A hash total is a detective control, not a preventive control. A hash total attempts to detect if numbers that are not normally added (such as account numbers) have been processed incorrectly. A batch total is used for numbers, such as dollars, that are normally added.
Choice "a" is incorrect. An echo check is a detective control, not a preventive control.