Final answer:
The active ingredient in a relaxer with a pH of 9.6-10.0 is Sodium hydroxide, also known as lye or caustic soda. It is a strong base used to break down protein bonds in hair.
Step-by-step explanation:
The active ingredient in a relaxer that has a pH of 9.6-10.0 is Sodium hydroxide (answer a). Sodium hydroxide, also known as lye or caustic soda, is a strong base with a high pH. It is commonly used in relaxer products to break down the protein bonds in hair, allowing for straightening or relaxing of the hair.
Other options mentioned in the question, such as ammonium thioglycolate, guanidine hydroxide, and calcium hydroxide, do not have a pH within the specified range.
For example, ammonium thioglycolate is commonly used in perms and has a pH around 8-9, while guanidine hydroxide has a pH around 13-14.