Afferent fibers carry information from the periphery to the central nervous system. In contrast, efferent fibers carry information from the central nervous system to the periphery. Generally, afferent fibers will carry sensory information and efferent fibers will carry motor and stimulatory information.

Afferent fibers in the digestive tract will detect changes in content and volume contained in the lumen of digestive organs. These signals are integrated in the central nervous system, and efferent signals are used to promote hormone or enzyme secretions and smooth muscle contraction.

Auerbach's plexus, also known as the myenteric plexus, is located between the gastrointestinal circular and longitudinal muscles, and controls motility throughout the system.

Secretion and blood flow in the gastrointestinal tract are both functions of the submucosal (Meissner's) plexus of the gastrointestinal system. Neither plexus is involved in hormonal balance. 

The vagus nerve is an essential part of the parasympathetic nervous system originating from the brain (cranial nerve X). The vagus nerve innervates the esophagus, stomach, pancreas, and upper portion of the large intestine. It is involved in parasympathetic stimulation of digestive function during periods of "rest and digest."

The rectum is innervated by the pelvic splanchnic nerves, which are also part of the parasympathetic nervous system.

We are told that bile salts can interact with both lipids and water in order to aid in the digestion and absorption of fats ingested in meals; thus, the bile salts are both hydrophobic (interact with the lipids) and hydrophilic (interact with water and polar molecules), giving them the definition of amphiphilic. An amphiphobic molecule would interact with neither polar, nor nonpolar molecules. 

Conjugation of the bile salts, made by the liver and stored by the gallbladder, enhances the ability of fat micelles to dissolve in water (hydrophilicity), prevents the bile salts from being trapped in the gastrointestinal lumen, and prevents pancreatic enzymes, like lipase and amylase, from degrading the bile salts. In phase II metabolism in the liver, conjugation increases the ability of a substance to be dissolved in water, which promotes aqueous solubility and excretion.

The gallbladder stores and concentrates bile from the liver. Bile is used to emulsify fats, assisting digestion in the small intestine. A person whose gallbladder has been removed should restrict fat consumption, as they will have a limited ability to digest fatty compounds. Triglycerides are a form of fat.

Triglycerides and cholesterol do not go straight into the venous circulation. These fats are made into structures called chylomicrons and are processed through lacteals into the lymphatic system.

Exercise can induce the release of corticoids which stimulate the sympathetic nervous system. This initiation will divert the body's resources and blood flow away from the digestive system, and toward the muscles that the athlete is engaging. As such, the meal will take a long period of time to digest.

The most important function of the large intestine is the resorption of water that comes from intake or the pancreas. Waste is still hydrated while in the small intestine.

The cell type that would be most likely to be directly responsible for producing stomach acid in Lorempis marengis is parietal cells. In humans, parietal cells, when stimulated by gastrin (produced by G cells), produce stomach acid. In the fictional organism, Lorempis marengis, we are told within the passage a great deal of information related to the structural and functional similarities between Lorempis marengis and humans in studies performed. The passage describes that the digestive tract of the fictional organism and humans is extremely similar based upon studies, and that it is assumed that at the cellular level they are similar as well. This question asks us to determine what cell type in the fictional organism would be most likely to be directly responsible for stomach acid production. As such, since we are told to assume that they are similar to humans at the cellular level, this question is really asking us what cell type in humans is most directly responsible for stomach acid production. The cell type most directly responsible for that in humans is the parietal cell, and therefore we can assume that that is true of Lorempis marengis as well.

While G cells produce gastrin, which stimulates acid production, the G cells do not directly produce the acid, so this is an incorrect answer choice.

Chief cells produce pepsinogen, a precursor enzyme to pepsin. They do not produce stomach acid.

Foveolar cells produce a mucus layer for the stomach. They do not produce stomach acid.

Enteroendocrine cells secrete a number of substances, including gastrin, histamine, endorphins, CCK, and somatostatin, but they do not directly produce stomach acid.