Final answer:
It is false that it is okay to have long fingernails and toenails in martial arts due to safety concerns. Nails are primarily composed of keratin. Historically, short staple cotton was less preferred than long staple cotton before the cotton gin made processing it easier.
Step-by-step explanation:
In martial arts, it is generally considered false that it is okay to have long fingernails and toenails. Long nails can cause injuries to both the person with the long nails and their training partners. Maintaining short, well-groomed nails is important for safety and hygiene in martial arts training.
The nail bed does not refer to the middle portion of the hard nail plate, so the statement is false. The nail bed is actually the skin underneath the nail plate. The middle portion of the hard nail plate does not have a specific name that is widely recognized.
Nails are composed mainly of a protein called keratin, which makes them strong and resistant. The other options listed, such as elastin, collagen, and melanin, serve different functions in the human body and are not the primary component of nails. Therefore, the correct answer is C. Keratin.
Regarding the historical context of cotton production, short staple cotton was actually less preferred to long staple cotton prior to the invention of the cotton gin. The cotton gin, which was invented by Eli Whitney in 1793, made it much easier to separate the cotton fibers from the seeds, especially in short staple cotton, which led to an increase in its demand and production.