Final answer:
Hair with a tight cuticle that makes it difficult for chemicals and moisture to penetrate has low porosity.
Step-by-step explanation:
Hair with a tight cuticle that makes it difficult for chemicals and moisture to penetrate has low porosity. The cuticle is the outermost layer of the hair shaft and acts as a protective barrier. When the cuticle is tightly packed, it prevents substances from entering the hair shaft, resulting in low porosity.