The stomach lining is made up of deep muscular grooves. how do you think these structures the stomach to break down food

The curves absorb the food and sort of squish it and make it easier to digest then the food goes into the stomach acid and kind of burns and become and little softer or in other words by allowing the stomach to stretch in order to accommodate large meals and get grip and move food during the digestion process.  

B. a graduated substance

Answerit is not a renewable energy source;