Answer: Choice B
Explanation: Fibrous joints are flexible.
When the skin is exposed to ultraviolet rays, the skin produces a molecule that is turned into Vitamin D.
Sun is the source of ultraviolet rays important for Vitamin D production. Due to this reason, in the case of Vitamin D deficiency, it is recommended by doctor's to absorb sunlight by skin. The Vitamin D production occurs specifically by UV B rays rays which lie in the range of 290-315 nanometer.
The chemical 7-dehydrocholesterol absorbs these rays and convert to previtamin D3. Further, previtamin D3 isomerizes to Vitamin D. Other than sunlight, Vitamin D can be taken through diet. The sources include seafood like fish, fish oil, dairy products, beef liver etc. Vitamin D is required for bone and teeth formation, muscle contraction, immune system etc.
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thanks, but can you post a grammar question i can answer thanks
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Good hygiene lowers your risk for diseases and illnesses commonly spread through viruses and bacteria. Your hands come into contact with bacteria every time you cough, use the restroom, touch your pet, or touch surfaces, such as stair railings, used frequently by others
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