Question

read the text.
the color of your hair depends on how much of each type of melanin, or pigment, it contains. all hair colors, from black to blond and everything in between, result from the blending of just two types of melanin: eumelanin (dark) and phaeomelanin (light). each hair grows out of an individual follicle, or tiny tube beneath the skins surface. pigment cells in the follicle inject melanin into the hair shaft as the hair develops and grows longer. in later years, the follicle slows its production of melanin. hairs with less melanin appear gray in color. if melanin production shuts down altogether, then the new hairs, lacking any melanin, will be white.
which organizational structure does this text primarily use?
problem - solution
cause - effect
compare - contrast

Explanation:

The text explains that hair color (effect) is due to melanin (cause). It further elaborates that as follicles slow melanin production (cause), hair turns gray (effect), and if melanin production stops (cause), hair becomes white (effect). This shows a cause - effect relationship.

Answer:

cause - effect