Answer:
Three treatments or reagents that causes protein denaturation are "heat", "urea" and "sodium hydroxide".
Step-by-step explanation:
Heat: when a protein is exposed to elevated temperatures its molecules vibrate so rapidly and violently that its bonds are disrupted. This causes that the protein loses its tertiary and secondary structures and finally causes its denaturation.
Urea: a chemical denaturing agents that denatures proteins by lower the protein melting temperature which has a similar effect that high temperature. Urea compets for hydrogen bond donors and acceptors which affects the protein stability.
Sodium hydroxide: sodium hydroxide is an alkali agent that increases the pH value of the protein's solution. This results in removing hydrogen-bond contributing protons of the protein, which breaks its hydrogen bonds and causes its denaturation.