If the oesophageal muscles are not working:

Correct Answer: C

Rationale: The correct answer is C because if the oesophageal muscles are not working, dysphagia to solids and liquids would occur. This is because the muscles are responsible for peristalsis, which is the wave-like contractions that push food down the esophagus. Choice A is incorrect because gravity alone cannot compensate for muscle dysfunction. Choice B is incorrect as water swallowing also requires proper muscle function. Choice D is incorrect as vomiting is not directly related to oesophageal muscle dysfunction.

Correct Answer: C

Rationale: The correct answer is C: small intestine. Primary carcinoma is least common in the small intestine due to its relatively lower exposure to carcinogens and slower cellular turnover compared to other segments like the colon. The esophagus is prone to carcinoma due to chronic irritation from acid reflux. The stomach is susceptible due to factors like Helicobacter pylori infection and dietary habits. The colon is at higher risk due to frequent exposure to fecal carcinogens. In summary, the small intestine has the least incidence of primary carcinoma due to lower exposure to risk factors.

Correct Answer: D

Rationale: The correct answer is D: Amylase. Gastric secretion does not contain amylase. Amylase is an enzyme produced by the pancreas and salivary glands to break down carbohydrates. In the stomach, gastric secretions mainly consist of hydrochloric acid (HCl) for digestion, intrinsic factor (IF) for vitamin B12 absorption, and mucous to protect the stomach lining. Therefore, amylase is not a component of gastric secretion.

Correct Answer: C

Rationale: The correct answer is C because during swallowing, the swallowing center in the medulla oblongata inhibits the medullary respiratory center to prevent aspiration. This coordination ensures that breathing is temporarily halted to prevent food or liquid from entering the airway. Choices A, B, and D are incorrect because not all processes of deglutition are under voluntary control, the vocal folds actually close to protect the airway during swallowing, and the movement of the food bolus down the esophagus is facilitated by peristalsis rather than gravity.

Correct Answer: B

Rationale: The correct answer is B: Break down proteins. Hydrochloric acid in the stomach helps to activate pepsin, an enzyme that breaks down proteins into smaller peptides. This process is essential for proper digestion of proteins. Choice A is incorrect because carbohydrates are broken down by amylase enzymes in the mouth and small intestine. Choice C is incorrect because emulsification of fats occurs in the small intestine with the help of bile. Choice D is incorrect as hydrochloric acid plays a significant role in the digestion of proteins in the stomach.