Final answer:
A body building conditioner (option c) is designed to penetrate the damaged hair shaft and deposit proteins into the cortex, which is essential for repairing and strengthening the hair from the inside out.
Step-by-step explanation:
The conditioner that can penetrate into the damaged hair shaft and deposit proteins into the cortex is the body building conditioner. These conditioners have protein-rich formulas that are designed to penetrate the hair cuticle and help to repair damage. They provide strength to the hair by filling in the weakened areas of the hair shaft, which can occur due to over-processing, heat styling, or environmental stressors.
An instant conditioner typically works only on the surface of the hair to detangle and add shine. A normalizing conditioner is often used after chemical treatments such as relaxers to restore the hair's natural pH level. However, for deep repair and to restore protein to the hair's cortex, the body building conditioner is usually the best choice.