Ann is an employee in the accounting department and would like to work on files from her home computer. She recently heard about a new personal cloud storage service with an easy web interface. Before uploading her work related files into the cloud for access, which of the following is the MOST important security concern Ann should be aware of?
A. Size of the files
B. Availability of the files
C. Accessibility of the files from her mobile device
D. Sensitivity of the files