Which of the following is most likely to stimulate gastric acid production?

Stress is known to stimulate gastric acid production primarily due to the activation of the body's stress response, which triggers the release of certain hormones, such as gastrin. Gastrin is a hormone produced by G cells in the stomach lining, and it plays a key role in promoting the secretion of gastric acid from parietal cells. When stress is present, the body may also enter a heightened state of arousal, leading to increased gastrin levels and, consequently, increased gastric acid secretion. This relationship helps explain why individuals under chronic stress might experience gastrointestinal issues, including acid-related disorders such as gastritis or peptic ulcers.

In contrast, a high-fiber diet is generally associated with improved gastrointestinal health and may not directly stimulate acid production. Physical activity can influence digestive processes in various ways, but it does not have a direct stimulatory effect on gastric acid secretion. Antibiotics, while potentially altering gut flora and affecting overall gastrointestinal health, do not stimulate gastric acid production directly. Hence, stress is the most relevant factor among the options provided that leads to increased gastric acid production.