Final answer:
Extremely curly hair having the thinnest and weakest sections at the twists is true, as these areas are structurally distinct due to the formation and positioning of keratin-filled cells within the hair shaft.
Step-by-step explanation:
The question asks whether it is true or false that extremely curly hair grows in long twisted spirals or coils, with the thinnest and weakest sections of the hair strands located at their twists. The correct answer is A. True. Hair is composed of keratin-filled cells that become highly structured into alpha-helices forming strong covalent disulfide bonds. When hair is permanently waved, these disulfide bonds are broken and reformed to create a new shape for the hair strand. The twists or coils in curly hair are indeed locations where the hair strand is thinner and may be weaker, which is a notion supported by the understanding of the hair's structure.
Each hair shaft is made from tightly packed keratinocytes and has three zones: the cuticle, cortex, and medulla. The hair we see is the hair shaft, which consists of dead cells, while the living part of the hair, the hair root, is within the follicle in the skin's dermis.
Temporary waves can also occur when water molecules disrupt hydrogen bonds in the hair's keratin strands. This explains why hair can take on a new shape temporarily after being wet and then drying into a different form as these hydrogen bonds re-form in new positions.