The answer is texture. Milady defines hair texture as the degree of coarseness or fineness of individual hair strands — a property that can genuinely vary across different parts of the same head, not just from client to client.
The other three choices are related but distinct hair properties tested elsewhere on the exam: density is how many strands grow per square inch, porosity is how readily the cuticle absorbs moisture or chemicals, and elasticity is how much a strand can stretch and still return to its original length. Texture is specifically about strand diameter.
Milady Standard Barbering, 6th ed., Ch. 10 (Properties and Disorders of the Hair and Scalp), p. 266: "Hair texture refers to the degree of coarseness or fineness of individual hair strands, which may vary on different parts of the head."
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: Which Conditioner Can Weigh Down Fine Hair, What Causes an Oily Scalp and Hair, How Often Are Eyebrows and Eyelashes Replaced, Which Hair Growth Phase Produces New Hair, 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.