The negative control used in the tests for protein, lipids, sugars, and starch was

Choice A rationale: Albumin solution is not a negative control, but a positive control for the test for protein. Albumin is a type of protein that reacts with the biuret reagent and produces a violet color. A positive control is used to confirm that the test works and gives a positive result when the substance is present³.

Choice B rationale: Starch solution is not a negative control, but a positive control for the test for starch. Starch is a type of carbohydrate that reacts with the iodine solution and produces a blue-black color. A positive control is used to confirm that the test works and gives a positive result when the substance is present³.

Choice C rationale: Glucose solution is not a negative control, but a positive control for the test for sugar. Glucose is a type of sugar that reacts with the Benedict's solution and produces a red-orange color. A positive control is used to confirm that the test works and gives a positive result when the substance is present³.

Choice D rationale: Olive oil is not a negative control, but a positive control for the test for lipids. Olive oil is a type of lipid that reacts with the Sudan III solution and produces a red color. A positive control is used to confirm that the test works and gives a positive result when the substance is present³.

Choice E rationale: Distilled water is a negative control for the tests for protein, lipids, sugars, and starch. Distilled water is a pure solvent that does not contain any of these substances. It does not react with any of the reagents and does not produce any color change. A negative control is used to confirm that there is no response to the reagent or the microorganism used in the test. It is used to set the baseline and verify that the detecting reagent is working properly³.

Choice A rationale: Isotonic is incorrect because isotonic is a type of solution that has the same concentration of water and solute as the cell placed in the solution. In an isotonic solution, there is no net movement of water across the cell membrane.

Choice B rationale: Osmotic is incorrect because osmotic is an adjective that describes the movement of water across a semipermeable membrane, not a type of solution. Osmosis is the process by which water moves from a region of high water concentration to a region of low water concentration.

Choice C rationale: Hypotonic is correct because hypotonic is a type of solution that has a higher concentration of water and lower concentration of solute than the cell placed in the solution. In a hypotonic solution, water moves into the cell and out of the solution by osmosis, causing the cell to swell.

Choice D rationale: Diffusive is incorrect because diffusive is an adjective that describes the movement of molecules from a region of high concentration to a region of low concentration, not a type of solution. Diffusion is the process by which molecules move across a membrane or a space due to their random motion.

Choice E rationale: Hypertonic is incorrect because hypertonic is a type of solution that has a lower concentration of water and higher concentration of solute than the cell placed in the solution. In a hypertonic solution, water moves out of the cell and into the solution by osmosis, causing the cell to shrink.