Human Health And Disease

Gastroesophageal reflux disease (GERD) occurs when the lower oesophageal sphincter (LES) fails to close properly, allowing stomach acid to flow back into the oesophagus. This reflux causes symptoms such as heartburn and chest pain, often mistaken for a heart attack. The LES acts as a barrier to prevent acid from rising, and when it remains open, it leads to acid reflux.

Thus, the correct answer is that the Lower oesophageal sphincter (LES) remains open.

The primary acid present in gastric juice is hydrochloric acid (HCl), which helps in digestion by breaking down food and activating digestive enzymes.