<span><span>The blood cells containing hemoglobin, that transports oxygen (O2) to the body tissues of vertebrates, are called red blood cells.</span> Red blood cells (RBCs), are also referred to as red cells, red blood corpuscles, haematids, erythroid cells or erythrocytes<span>, (from Greek erythros for "red" and kytos for "hollow vessel"..RBCs take up oxygen in the lungs and release it into tissues while squeezing through the body's capillaries.</span></span>
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<span>Chlorofluorocarbons
(CFCs) chemicals contain carbon, chlorine and fluorine and is t so expensive at
the same time it’s not flammable, the reason why it is mainly used in business
such as refrigerators and plastics. However, these chemicals destroys our
stratosphere, the second layer of the Earth’s atmosphere and protects us by
blocking the ultraviolet radiation (UV Light). This type of radiation can seep
through organisms skins and can leave destructive effects on DNA molecules
which will also cause skin cancer.</span>
<span>The elements that are found in a high proportion in Earth's crust are oxygen, aluminium, iron, calcium, potassium, sodium, and magnesium. But for your Option, I think it is B) Oxygen and Silicon. This is because Oxygen makes 46.6% while Silicon makes 27.7% of the Earth crust.</span>
