Which of the following is a key indication of chemical damage to hair?

Extreme brittleness and loss of elasticity are significant indicators of chemical damage to hair. Chemical treatments, such as hair coloring, perming, or relaxing, can break down the hair’s protein structure, leading to increased brittleness. When hair loses elasticity, it becomes less flexible and prone to breakage, exhibiting a lack of resilience compared to healthy hair. Elasticity is crucial for maintaining the hair's ability to stretch without snapping. Therefore, observing these signs in hair often suggests that it has undergone chemical treatments that may have compromised its structural integrity and overall health.

In contrast, shininess and softness are characteristics of healthy hair and not indicative of damage. Vibrant color retention suggests the hair has been properly cared for and is not experiencing chemical damage. Moisture retention is a sign of healthy hair as well, indicating that the cuticle layer is intact and able to hold moisture effectively. These other options reinforce the idea of hair health rather than damage, making extreme brittleness and loss of elasticity the correct choice.