Final answer:
Sodium hydroxide (lye) is the relaxer that may render hair unsuitable for any additional chemical service.
Step-by-step explanation:
The relaxer that may render hair unsuitable for any additional chemical service is sodium hydroxide (option b).
Sodium hydroxide, also known as lye or caustic soda, is a strong alkali that is commonly used in relaxers to break down the disulfide bonds in hair. These bonds give hair its shape and strength. However, sodium hydroxide is highly reactive and can cause severe damage to the hair if not used properly.
When applied to the hair, sodium hydroxide alters the structure of the hair shaft, making it more vulnerable to further chemical treatments. This means that if sodium hydroxide is used as a relaxer, it may make the hair unsuitable for any additional chemical services, such as coloring or perming, as these treatments could further weaken and damage the hair.