Question

you tested for the presence of four different nutrients by adding indicators the three test tubes. complete if the mystery food sample contained the nutrient, then it would change to the same color as the positive control. complete in this lab, the only test that turned out positive was for dropdown options: proteins., lipids., polysaccharides., monosaccharides. done

Explanation:

In typical food nutrient testing labs (like using indicators for nutrients), if the context is a standard lab activity (e.g., using Biuret test for proteins, Sudan for lipids, iodine for polysaccharides, Benedict for monosaccharides), and the dropdown shows "proteins" as the selected positive test here, we assume this is the correct choice based on the lab's result (as per the interface showing "proteins" highlighted and the lab's positive test outcome).

Answer:

proteins.