Final answer:
Developer is used to diffuse, dissolve, or decolorize natural or artificial pigment.
Step-by-step explanation:
The correct answer is b) Developer. Developer is used to diffuse, dissolve, or decolorize natural or artificial pigment. In the context of hair dye or hair color, a developer is a substance that activates the dye and helps it penetrate the hair follicles. It is typically used in combination with hair bleach or hair color to achieve the desired hair color or tone.