There are 115 known elements as of today (Feb. 13, 2016)
so, 'C' is the correct answer
Answer:
A closed system is a physical system that does not allow transfer of matter in or out of the system, though, in different contexts, such as physics, chemistry or engineering, the transfer of energy is or is not allowed.
Explanation:
Norepinephrine<span> (</span>NE<span>), also called </span>noradrenaline<span> (</span>NA<span>) or </span>noradrenalin<span>, is an </span>organic chemical<span> in the </span>catecholamine<span> family that functions in the </span>brain<span> and </span>body<span> as a </span>hormone<span> and </span>neurotransmitter. The name "noradrenaline," derived from Latin roots meaning "at/alongside the kidneys," is more commonly used in the United Kingdom; in the United States, "norepinephrine," derived from Greek roots having that same meaning, is usually preferred.<span> "Norepinephrine" is also the </span>international nonproprietary name<span> given to the </span>drug.<span>Regardless of which name is used for the substance itself, parts of the body that produce or are affected by it are referred to as </span>noradrenergic<span>.</span>
4. 4 C + S8 = 4 CS2
5. H2 + O2 = H2O2 is already balanced.
6. 4 Na + O2 = 2 Na2O
Answer: There are both natural and human sources of carbon dioxide emissions. Natural sources include decomposition, ocean release and respiration. Human sources come from activities like cement production, deforestation as well as the burning of fossil fuels like coal, oil and natural gas.
Explanation:
