Answer:
Stem cells provide new cells for the body as it grows, and replace specialised cells that are damaged or lost. They have two unique properties that enable them to do this: They can divide over and over again to produce new cells. As they divide, they can change into the other types of cell that make up the body.
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Spiders have malpighian tubules<span> to absorb salts and wastes while humans have microscopic subunits in the kidneys called </span>nephrons to filter blood. Malpighian tubules<span> remove wastes from insects by producing urine and solid nitrogenous waste, which are then excreted from the body.</span>
In Emphysema, one form of chronic obstructive pulmonary disease (COPD), alveolar walls breakdown, alveoli fuse creating more open spaces, and the lungs lose their elasticity. The result is "trapped air" which becomes difficult to expel upon expiration, thus an expiratory condition.
The correct answer is A. "A sperm cell and an egg cell combine to form an embryo."
