Final answer:
The primary actions in the small intestine are peristalsis and enzyme secretion, which aid in food movement and digestion respectively.
Step-by-step explanation:
Primary Muscular and Chemical Actions in the Small Intestine
In the small intestine, the primary mechanical movements are segmentation and peristalsis. Segmentation is characterized by localized contractions of the circular muscles that mix the chyme with digestive juices and facilitate the process of absorption. Meanwhile, a type of peristalsis known as migrating motility complexes propels residual chyme towards the large intestine. The chemical actions include the secretion of digestive enzymes by the pancreas and the intestinal walls, which help break down food components into absorbable nutrients. Additionally, bile secretion plays a crucial role in the small intestine by emulsifying lipids, aiding in their digestion. To answer the question directly, b) Peristalsis and enzyme secretion best describes the primary muscular and chemical actions occurring in the small intestine.