Answer:
Natural factors of population change can't be swayed by humans. So for an example of a natural factor take an Earthquake. As of right now we can only predict when Earthquakes will. Inevitably some things will still get damaged and that just can't be helped. An Artificial factor for population change is something specifically made by humans. For an example take a genocide. If some guy decides he wants to go on a killing spree, well all I can say is that is Definitely not natural. Hope that helped.
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Protein is the best nutrient
Answer:
Varicose veins can best be described as veins cannot prevent the backflow of blood.
Explanation:
Varicose veins are a manifestation of venous insufficiency or peripheral vascular insufficiency.
Veins are blood vessels that, unlike arteries, are not able to contract, so they depend on gravity, muscle contractions and a system of valves to be able to carry blood to the heart.
<u>When the venous valves do not work, the blood is not transported properly, backflow occurs and is retained, producing dilation of the vein walls, which is characteristic of varicose veins</u>. In this case, veins cannot prevent the backflow of blood.
The other options are not correct because:
- <em>Varicose veins do not lose their ability to transport blood.
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- <em>Veins cannot be used to transport blood from the heart.
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- <em>Failure to adequately transport waste to the heart does not apply in this case.</em>
