Answer:
The answer is A.
Step-by-step explanation:
Heartburn happens because stomach acid becomes backed up in the esophagus, which moves food from your mouth to your stomach.
The burning sensation is usually the result of stomach acid leaking up into the esophagus through a flaw in a valve known as the lower esophageal sphincter (LES), which connects the esophagus and the stomach. When the LES doesn't tighten properly or becomes weakened, stomach acid can flow back into the esophagus, causing a burning feeling.