Gi regulatory substances part 2

What is the primary function of glucagon-like peptide (GLP-1) in the gastrointestinal system?

1: Stimulates peristalsis in the stomach and small intestine
2: Increases intestinal water and electrolyte secretion in response to vagal stimulation
3: Increases insulin release in response to oral glucose
4: Increases gastric acid secretion in response to stomach distension