Which process occurs primarily in the small intestine?

The process that occurs primarily in the small intestine is digestion and absorption. The small intestine is specifically designed for these functions, as it has a large surface area due to the presence of villi and microvilli, which facilitate the breakdown of food and the absorption of nutrients into the bloodstream.

During digestion, enzymes break down carbohydrates, proteins, and fats into smaller molecules that can be absorbed. The small intestine's walls contain specialized cells that transport these nutrients into the body. This process is critical for providing the body with essential nutrients, vitamins, and minerals necessary for energy, growth, and overall health.

The other processes mentioned, such as filtration, detoxification, and excretion, primarily occur in other parts of the body. For example, filtration is typically associated with the kidneys, detoxification primarily occurs in the liver, and excretion refers to the elimination of waste products through the kidneys and intestines. Hence, the small intestine's main roles focus on digestion and absorption, making it the correct answer in this context.