Based on the data, was zack, who ate the tofu, guilty of leaving a mess in the classroom?

Zack could not have made the mess because he ate Tofu which contains proteins.

Zack brought Tofu to the classroom and it contains protein.

The unknown food sample was tested for protein by:

The unknown food sample did not turn pink/purple so it did not contain proteins which is what Zack had in his tofu.

In conclusion, Zack could not have made the mess because the test did not indicate the presence of protein in the mess.

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for example, no new evidence will demonstrate that the earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the earth is not divided into solid plates that have moved over geological timescales .