Which of the hormones is not produced by the argentaffin cells?

The correct option is D Gastrin
Certain types of enteroendocrine cells are located at the basal part of the gastric glands. They are of two types: argentaffin cells and gastrin or G cells. The hormones secreted by argentaffin cells and G cells are summarised below:

Serotonin is a powerful smooth muscle stimulant and plays a role in stimulating peristaltic activity of the intestine.
Somatostatin regulates the secretion of gastrointestinal hormones.
Histamine plays a role in gastric secretion by inducing the production of acid in the stomach. It also helps in dilating blood vessels supplying to that area.
Gastrin is a hormone produced by G-cells. It is responsible for enhancing gastric mucosal growth, gastric motility, and secretion of hydrochloric acid (HCl) into the stomach.