What are the primary mechanisms that slow gastric emptying when fatty chyme enters the duodenum?

e) Fatty substances entering the duodenum release CCK and trigger enterogastric nervous reflexes.

Explanation:
When fatty chyme enters the duodenum, it stimulates the release of the hormone cholecystokinin (CCK). CCK inhibits gastric motility and contraction of the pyloric sphincter, thereby slowing gastric emptying. Additionally, the presence of fat in the duodenum activates the enterogastric reflex, a nervous reflex that also inhibits gastric motility and emptying, allowing more time for fat digestion and absorption in the small intestine.

The final answer is $e$