I have a 2012 macBook Pro 13" and the option "Use audio port for" does not appear at all in the sound menu. why is this? im running mountain Lion 10.8.2

Because line-in has been removed.

It does allow for an Apple headset with mic., but I don't know if it would work with third-party ones.

You'll need to use a Griffin iMic or similar to use line-in via a USB port.

The same goes for the 15" retina, the newest MBA and the new iMac (whenever it finally arrives).

Try plugging in a headphone, or a 3,5mm jack cable,click output tab and see if it pops up.

If not conntact Apple support, go to the Apple store

You have to be kidding me, that counts me out for buying a 13" for light duty audio work. Not a smart move in my opinion, as everyone I know in the pro audio world uses macs. I can see many saying...not me! WOW, at least the 13" I have now has what I consider half a audio function, compared to my 15". Now a new 13" is TOTALLY out of the question.

By the look of it, you can add the new iMacs to the tally.