The answer is elasticity. Milady's haircoloring-consultation section states that elasticity is an indication of the strength of the cortex — including its cross-bonds and melanin molecules — which is why colorists check it before a service.
The book adds a concrete benchmark: normal elasticity is indicated by wet hair that can stretch up to 50 percent of its original length and return without breaking. Texture, density, and porosity are all real hair-property terms, but none of them is defined as a direct read on cortex strength the way elasticity is.
Milady Standard Barbering, 6th ed., Ch. 18 (Haircoloring and Lightening), p. 643: "Elasticity is an important factor to consider because it is an indication of the strength of the cortex, including cross-bonds and melanin molecules."
This is 1 of the real Hair Science questions in FadeJunkie's Milady-sourced 300-question bank. See the Hair Science practice questions page for a fuller sample, or try the Hair Science practice quiz and flashcards for free. A one-time $15 lifetime pass unlocks the complete question bank across all 13 tested topics.
More real Hair Science questions with sourced answers: What Does Reduced Melanin Production Cause, What Color Pigment Is Missing From White Hair, What Hair Type Has a Raised Cuticle That Absorbs Chemicals, Which Hair Layer Gives Strength, Elasticity, and Color, and 28 more on the Hair Science practice questions page.
Browse every topic on the Practice Question Hub, or see the Texas Barber State Board Exam Guide for the full exam process — required hours, PSI scheduling, and fees.