The correct answer is D) A 3 oz. portion of meat is approximately the size of a deck of cards.
Here are some other examples to help you understand how big portions should be for other foods:
Links:
[1] http://takingcharge.csh.umn.edu/sites/default/files/images/thumbnails/cards.jpg
[2] http://takingcharge.csh.umn.edu/create-healthy-lifestyle/diet-nutrition/more-about-dietary-guidelines-and-your-health