Answer : 3. "Ctrl + N"
Explanation :

1. In Microsoft Word, Excel, and PowerPoint, the shortcut key to open a new document or window is Ctrl+N. Pressing this key will open a new document or window.

2. If you want to open a specific type of document, you can select a specific document type following the Ctrl+N key combination. For example, if you want to open a new Word document, you can select Word Document followed by the Ctrl+N key combination.

3. Here are some other shortcut keys that can be used to open a new document or window-

- Ctrl+O: Open an existing document

- Ctrl+S: Save the current document

- Ctrl+P: Print the current document

- Ctrl+X: Cut selected content

- Ctrl+C: Copy selected content

- Ctrl+V: Paste selected content

- Ctrl+Z: Cancel previous action

- Ctrl+Y: Redo the previous action