In Windows OS, in order to permanently delete a file from the computer, which of the following keys should be pressed ?

The correct answer is (d) Shift + Delete.

When you delete a file using the Delete key, it is moved to the Recycle Bin. You can empty the Recycle Bin to permanently delete the files. However, if you use the Shift + Delete keys to delete a file, it is permanently deleted without being moved to the Recycle Bin. This means that you cannot recover the file later.

The other options are incorrect. Ctrl + Delete opens the Task Manager. Alt + Delete opens the Windows Security menu. Delete + Delete is the same as pressing the Delete key once.