A protein conditioner is effective for

• A. Slightly increasing hair diameter
• B. Restoring color
• C. Repairing split ends
• D. Increasing curl moisture

Answer: (A)

Protein conditioners work by depositing proteins onto the hair shaft, which helps reinforce the hair and fill in tiny gaps in the cortex while smoothing the cuticle. This reinforcement adds slight bulk to each strand, so hair may feel and look a bit thicker or fuller—the reason this option is the best fit. In contrast, color restoration isn’t achieved with conditioner, split ends aren’t truly repaired by sealing alone (they require trimming for a permanent fix), and moisture-focused benefits for curls come from hydrating products rather than protein deposits. The effect of protein conditioners is typically temporary and depends on the specific product and hair condition.