Which of the following is known as a neutralizer or stabilizer in hair treatments?

The term "neutralizer" or "stabilizer" in the context of hair treatments most accurately refers to an oxidizing agent. Neutralizers are used particularly in chemical processes such as perming or relaxing to stop the action of the chemical solution and to help reform the hair's disulfide bonds into their new shape.

In the process of perming, for example, the hair is first treated with a reducing agent that breaks down the keratin structure, allowing for curl formation. The oxidizing agent then comes into play to neutralize the process, ensuring that the hair maintains its new shape and preventing the hair from reverting back to its original form. This stabilization is crucial for the longevity of the treatment's effects.

Other options, while related to hair care, do not serve the same function as neutralizers. A thio relaxer is a specific type of hair treatment that alters the hair’s structure but is not used as a neutralizer itself. A color developer typically contains an oxidizing agent used during the hair coloring process, but it does not perform the role of a stabilizer in the same way. A moisturizer is beneficial for maintaining hair health but does not have the chemical properties required for neutralizing or stabilizing hair treatments.