Epithelial surfaces provide the first line of defense against infection by the use of several types of mechanisms. One of the chemical mechanisms used by epithelia is:

Correct Answer: B

Rationale: Antimicrobial peptides are chemical defenses; tight junctions are physical, mucus and cilia are mechanical.

Correct Answer: A

Rationale: An eyeball that is too short causes farsightedness (hyperopia) because light focuses behind the retina, making near objects blurry.

Correct Answer: C

Rationale: Histamine is released by damaged cells (e.g., mast cells) to initiate inflammation, unlike interferon (antiviral), complement (immune enhancement), or antihistamine (blocks histamine).

Correct Answer: A

Rationale: Monoclonal antibodies come from hybridomas (B cell-tumor cell fusions), producing identical antibodies, not from pregnancy, infection, or B-T cell fusion.

Correct Answer: D

Rationale: C3a and C5a are anaphylatoxins that trigger inflammation by recruiting immune cells, not forming MAC (C5b-C9) or opsonizing (C3b role).