Final answer:
The main jobs of the large intestine are water absorption and waste elimination, as this organ is crucial for reabsorbing water and mineral salts, as well as storing and eliminating waste material.
Step-by-step explanation:
The main jobs of the large intestine are to absorb water from the undigested food material, process this material, and prepare it for elimination from the body. The large intestine, which includes the cecum, colon, and rectum, is shorter in length but larger in diameter compared to the small intestine. Notable functions of the large intestine include the reabsorption of water and mineral salts, the storage of waste material, and playing host to intestinal flora which aid in the digestion process.
Based on the options provided, the most accurate answer is A. water absorption and waste elimination. This is because the main functions of the large intestine encompass the extraction of water and mineral salts from undigested food and the storage and subsequent elimination of waste material. The large intestine also participates in the synthesis of certain vitamins and supports a variety of microbes beneficial to the digestive system.