Concept:Lice are external parasites that attack the skin and hair of livestock.Explanation:When lice infest an animal, they bite or feed on the skin surface.This causes intense irritation and a constant urge to scratch.Affected animals repeatedly rub or bite their body to relieve the discomfort.Therefore, itching is the most direct and typical symptom.Abdominal pain, profuse salivation, and blood oozing are not linked to louse infestation.Answer:A. itching of the body