Final answer:
Collagen is correctly matched with proteins; it is a fibrous substance in connective tissues. Lactose is a sugar not a lipid, hemoglobin is a protein not a carbohydrate, and hydrochloric acid is not a nucleic acid.
Step-by-step explanation:
The molecule that is correctly placed with the category to which it belongs is A. Collagen---protein. Collagen is a fibrous protein that is found in connective tissues of animals, providing structural support. The other pairs listed are incorrect: B. Lactose is a disaccharide sugar, not a lipid; C. Hemoglobin is a protein that carries oxygen in the blood, not a carbohydrate; and D. Hydrochloric acid is a simple inorganic compound, not a nucleic acid.
Collagen is typically found in the extracellular matrix and is crucial for holding cells together, providing strength and elasticity. Proteins, such as collagen, are one of the four major classes of organic compounds, alongside nucleic acids, carbohydrates, and lipids. Knowing this can help you determine that the other options provided are in the wrong categories.