Vitamin D is a <span>fat-soluble </span>vitamin that <span>helps regulate the amount of calcium and phosphate in the body. </span><span>The recommendation for dietary allowance for Vitamin D for different categories of people are based on scientific research, publications, traditional use, or expert opinion. </span>Recommended daily allowance (RDA) is 600 International Units (IU) for those 1-70 years of age. Here belong also individuals around 20 years of age, so their recommended dietary allowance is also 600 IU.
<span> cells maintain homeostasis as they are living things. The main way cells maintain homeostasis is through their cell membranes. Cell membranes protect the cell from the outside world, if there is too much of something in the cell, the cell membrane uses pockets to expel some of it, it trasports nutrients across the cell, and it also dictates what goes in and out of the cell. Those are some ways a cell maintains homeostasis. And all living things must maintain homeostasis</span><span>: <span>Regulate intracellular ion control (e.g. maintain very specific [Ca^2+] levels)
Regulate extracelluar to intracellular ion transport. E.g. for maintaining water and blood pressure via the kidneys.
Regulate metabolism, for temperature control (e.g. in brown adipose tissue).
Regulate transcription and translation, for hormone release and
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The characteristic that best represents good walking technique is letting your arms swing loosely and your feet so they move fluidly and finding great balance so you last longer. So the best answer to your question is letter D. I hope this helps.