Answer:
B. Nuclear energy
this type of energy splits nuclei or combines them.
Valves ensure blood flows toward your heart. Vein valves work to bring the blood that flowed down via arteries back up to your heart.
C) I and III only just got this question on usa test prep and therefore i'm right
Changes in the amount of sea ice can disrupt normal ocean circulation, thereby leading to changes in global climate. Even a small increase in temperature can lead to greater warming over time, making the polar regions the most sensitive areas to climate change on Earth
Answer:
A: Oxygen levels are low and, therefore, more red blood cells are produced, giving the athletes an advantage when competing at lower altitudes.
Explanation:
<em>At high altitudes, the partial pressure of oxygen is lower compared to lower altitudes</em>. The body system try to adjust to lower oxygen level by undergoing several physiological changes. Depending on the duration spent in high altitude, the body can either try to adjust in the short term or acclimatize for a longer term.
One of the processes the body undergoes during acclimatization is an increase in red blood cell production. The kidney secretes erythropotein in response to inadequate oxygen in body tissues, and this makes the liver to increase erythrocyte production.
The increase in red blood cell production correspondingly increases the oxygen-carrying capacity of the blood as a result of increased hemoglobin. This condition persists for a few weeks even after the body returns to lower altitude where oxygen is adequate. Increased oxygen capacity means the rate of energy production (through respiration) within the body will also increase
<em>Hence, those who acclimatize to high altitude usually experience increased capillary density, tissue perfusion and improved athletic performance at lower altitudes. </em>
The correct option is A.
