Concept:Defects of vision are corrected using lenses of specific focal lengths, depending on the type of defect.Explanation:Statement I is correct because it accurately describes a common vision defect and its correction.Statement II is correct as it also correctly identifies another vision defect and its appropriate correction.Statement III is incorrect because short-sightedness (myopia) is corrected by using a suitable concave or diverging lens, not a convex lens.Therefore, only statements I and II are correct.Answer:C. I and II only.