Small intestine can be best described a. thin tube that carries food from the mouth to the stomach b. muscular opening at the end of the large intestine c. small tubular organ where digestion of food and absorption of nutrients occurs d. large tubular organ that removes water from the digestive tract

The answer to this is C.

In the small intestine, it consists of duodenum and ileum in simple. The duodenum is where most food is digested. Enzymes are secreted and they break down complex and insoluble food into simple small soluble molecules.
After digestion, the food will be absorbed into the body in the ileum. The food flow from the ileum into the body cells by diffusion and active transport. Villi is also present in the small intestine to help the absorption process. After absorption, the nutrients would be transferred into the cells that needed.
The rest of the food that is not absorbed is trasferred to the large intestine to re absorb the water. After that, they're feaces and they'll be egested

Hydrosphere is the correct answer