Correct Answer: A. UVA

Explanation: UVA (315-400 nm) is the major contributor to drug-induced photosensitivity. Common drugs causing phototoxic eruptions include tetracyclines, furosemide, thiazides, sulfonamides, NSAIDS, oral retinoids, amiodarone and phenothiazines. UVB (290-315 nm) is more erythemogenic and associated with photocarcinogenesis.

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Reference: Bjellerup M, Ljunggren B. Differences in phototoxic potency should be considered when tetracyclines are prescribed during summer-time. A study on doxycycline and lymecycline in human volunteers, using an objective method for recording erythema. Br J Dermatol. 1994; 130:356-60