a because the marble changed its position quickly meaning that it was in motion
Explanation:
B. Spindle fibers begin to form.
<span>The organs that participate in vitamin D synthesis and activation are kidneys and liver.
</span>Vitamin D<span> is carried in the bloodstream to the </span>liver, where it is converted into the prohormone calcifediol.<span>Calcifediol is further hydroxylated by the kidneys to form </span>calcitriol and c<span>alcitriol circulates as a hormone in the blood, and regulates the concentration of </span>calcium<span> and </span>phosphate.
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Multicellular organisms are able to achieve homeostasis because they cells are specialized in function and work cooperatively with one another.
Letter d)
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