Four groups of scientists, in different parts of the world, are dating fossils found in a rock layer of the same geologic time period. to validate the age of their fossils, the results of their tests would need to be

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explanation:

sulfur dioxide

explanation: acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. these substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.

the sun's light combined with the visible wavelenghts form what is called ultraviolet radiation, which are the long waves at the end of a visible light sprectrum.

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