Concept:An aldohexose is a monosaccharide containing six carbon atoms and an aldehyde group.Explanation:Glucose has six carbon atoms and an aldehyde group, so it is an aldohexose.Ribose is an aldopentose.Fructose is a ketohexose.Lactose is a disaccharide.Hence, among the given options, only glucose fits the definition.Answer:Option D. Glucose