An accounting department uses a spreadsheet to calculate sensitive financial transactions. Which of the following is the MOST important control for maintaining the security of data in the spreadsheet?

A. There is a reconciliation process between the spreadsheet and the finance system.
B. The spreadsheet is locked down to avoid inadvertent changes.
C. A separate copy of the spreadsheet is routinely backed up.
D. Access to the spreadsheet is given only to those who require access.