The anwser is true. Exposure to ultraviolet rays can cause skin cells to produce melanin which darkens the surface of your skin into a suntan.
The answer is radioactive dating
The Nervous system of the body consists of all the nerve cells. It is the body's "speedy" electrochemical communication system.
every neuron (nerve cell) has a long process known as 'axon' which is used to contact the next cell in the circuit. The receiving cell (another neuron) has small processes called 'dendrites' which are contacted by the axon. Now the neurons, like all other cells in the body, are enclosed by a selectively permeable cell membrane - which means it allows certain chemicals to pass through, while others are prevented from entering or leaving the cell
Is this a bunch of typos or did you put this question in a different language?
Carbon dioxide can be transported through the blood via three methods. It is dissolved directly in the blood, bound to plasma proteins or hemoglobin, or converted into bicarbonate.
The majority of carbon dioxide is transported as part of the bicarbonate system. Carbon dioxide diffuses into red blood cells. Inside, carbonic anhydrase converts carbon dioxide into carbonic acid (H2CO3), which is subsequently hydrolyzed into bicarbonate (HCO3−) and H+. The H+ ion binds to hemoglobin in red blood cells, and bicarbonate is transported out of the red blood cells in exchange for a chloride ion. This is called the chloride shift.
Bicarbonate leaves the red blood cells and enters the blood plasma. In the lungs, bicarbonate is transported back into the red blood cells in exchange for chloride. The H+ dissociates from hemoglobin and combines with bicarbonate to form carbonic acid with the help of carbonic anhydrase, which further catalyzes the reaction to convert carbonic acid back into carbon dioxide and water. The carbon dioxide is then expelled from the lungs.
