Question

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

Explanation:

The text states the only positive - test in the lab was for a specific nutrient, and the option 'proteins' is the correct one among the given choices.

Answer:

proteins