What allows users to see and change the contents and properties of files?

The correct choice allows users to see and change the contents and properties of files, which is an essential capability in file management. When a user has modify permissions, they are granted the ability to make alterations to the file's content and properties. This includes editing the file, deleting it, or saving changes made to it, thus providing a high level of control over the file.

While permissions like Read allow users to view file contents, they do not enable any changes. Similarly, Write permits users to add new data or append to a file without necessarily allowing for modifications of existing content. Full Control encompasses all permissions, including modifying, but is broader as it also includes changing permission settings for the files. In this context, Modify is the most precise choice for indicating the ability to see and change the contents and properties of files specifically.