Which NTFS permissions should you assign if the user should be able to create folders and files and open files to read data but not delete files?

To allow a user to create folders and files, and read data from files without the ability to delete them, you should assign the user the "Modify" permission, which includes creating and reading files, but not the "Delete" permission. Additionally, you can assign "List folder contents" permission to enable browsing the folder. It's also important to ensure that the "Delete" permission is explicitly denied if inherited permissions would otherwise allow it.