Which of the following is a sign of excessive tension from hair extensions?

Redness or irritation on the scalp is an indicator of excessive tension from hair extensions. When extensions are applied too tightly, they can cause stress on the hair follicles and scalp. This stress may lead to inflammation, resulting in redness, irritation, or even pain. It is crucial for stylists to monitor the tension applied during the installation of hair extensions, as excessive tension can potentially harm the client's hair and scalp health.

In contrast, shiny and smooth hair indicates proper care and maintenance, frequent styling without damage suggests the extensions are well-placed and not causing strain, and a long-lasting hold of the style does not necessarily indicate any issues with tension. Each of these alternatives reflects a positive outcome rather than potential problems.