Keyboard Shortcut for Third Option ("Don't Save")

[polycat33]

I was wondering if anyone knows of a keyboard shortcut for choosing the third option in a lot of popup windows (that have three options). One thing is highlighted and you can press return to choose it, and you can also choose cancel by hitting option+period. But what about that third option, for example, if you try to exit something without saving you'll have "don't save," "cancel," and "save." Is there a keyboard shortcut to select the don't save option, or whatever the third option may be?

 

[apfhex]

Command d