I think it would be kidneys because of the way the question is worded, kidneys are the only things you have 2 of that also is involved in the digestion of foods.
My greatest fear would have to be getting stuck in an elevator.
Did you mean mechanical ? If you do mean mechanical then here's the answer to your question:
Mechanical digestion is when the food is being broken down physically into smaller pieces from the mouth and chemical digestion is when the food is being broken down into substance particals starting from the saliva and proceeding through the small intestines.
