The correct answer is C. Mouth.
Digestion is the process of breaking down food into smaller molecules that can be absorbed by the body. It begins in the mouth, where food is chewed and mixed with saliva. Saliva contains enzymes that start to break down carbohydrates. The tongue helps to move the food to the back of the throat, where it is swallowed.
The food then travels down the esophagus to the stomach. The stomach is a muscular sac that churns and mixes the food with gastric juices. These juices contain enzymes that break down proteins and fats. The stomach also produces hydrochloric acid, which kills harmful bacteria in the food.
After about two hours, the partially digested food leaves the stomach and enters the small intestine. The small intestine is a long, coiled tube that is about 20 feet long. It is lined with millions of tiny finger-like projections called villi. The villi increase the surface area of the small intestine, which allows it to absorb nutrients from the food.
The nutrients are absorbed into the bloodstream and carried to the liver. The liver stores some of the nutrients and releases them into the bloodstream as needed. The other nutrients are used by the body for energy or to build new cells.
The undigested food leaves the small intestine and enters the large intestine. The large intestine is about five feet long. It absorbs water from the food and stores the waste products until they are eliminated from the body.
The process of digestion takes about 24 hours. It is a complex process that is essential for the body to get the nutrients it needs to function properly.