Which explains the basis of the biuret test?
a) sudan iii dye binds to lipids and changes color
b) a blue dye binds to protein and changes color
c) under base conditions, copper ions bind to the amino groups of proteins and change color
d) iodine fits into the coils of starch polymers and changes colors

The correct answer is C) under base conditions, copper ions bind to the amino groups of proteins and change color. This test is a chemical one, which means it's testing the chemical properties of an object, specifically to detect peptide bonds. When these bonds are detected, an ion called copper II will bind (as the answer indicates), and will change the blue color of biuret into a violet color.

The correct answer is c