The answer is C. Photosynthesis Reaction. Hopes this helps :D
The statement which best explains why carbon is present in so many kinds of molecules is because <u>it can form four covalent bonds.
<em /></u>It isn't rare on Earth, so A is incorrect. It has valence electrons, so C is incorrect. It cannot become an ion, so D is incorrect.<u>
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The pyloric sphincter is compose of smooth muscle and is located between the pylorus in the stomach and duodenum of the small intestine. In digestion, it serves as a valve controlling the flow of food thus it prevents the contents of small intestine backing up into the stomach.
<span>The burners must be turned off because, in the case of liquid chromatography, the eluant solvents being used are flammable. Leaving the burners lit could cause the eluant to catch on fire, putting the scientist at risk.</span>