Carcinoid tumor, Is tumor of:

Correct Answer: B

Rationale: Carcinoid tumors arise from enteroendocrine (APUD) cells, which secrete hormones like serotonin.

Correct Answer: A

Rationale: Sieve plates are clusters of fenestrae in the endothelium of hepatic sinusoids, allowing plasma exchange with the space of Disse.

Correct Answer: B

Rationale: Pepsin is not a component of saliva; it is found in the stomach where it helps digest proteins. Saliva contains mucin, amylase, and IgA antibodies.

Correct Answer: A

Rationale: Mucus secreted by gastric cells forms a protective barrier against HCl, preventing damage to the stomach lining.

Correct Answer: A

Rationale: The frenulum is a fold of tissue that anchors the tongue to the floor of the mouth.