Final answer:
The main ingredient in an alkaline perm is ammonium thioglycolate, which breaks and reforms the disulfide bonds in hair during the perming process. The correct multiple-choice option is (a).
Step-by-step explanation:
The main ingredient in a cold or alkaline perm solution is ammonium thioglycolate. This chemical acts to break the disulfide bonds within hair's keratin structure during the perming process, allowing the hair to take on a new shape when wrapped around perm rods. After application, the hair is neutralized, re-forming the disulfide bonds into their new shape. It should be noted that sodium hydroxide is a strong base used in chemical hair straightening treatments, and not typically in perming solutions, which usually contain a reducing agent like ammonium thioglycolate rather than a strong base. The correct multiple-choice option is (a).