Concept:Isomers have the same molecular formula but different structural arrangement.Explanation:C3H8O is the formula for both propan-1-ol and propan-2-ol.Propan-1-ol has the −OH group on carbon 1, while propan-2-ol has it on carbon 2.Thus, they are positional isomers.Answer:1-propanol and 2-propanol. Option A is correct. (Option D repeats the same pair in reverse order.)