Answer:
Carbon
Explanation:
Carbon has four electrons in its valence shell, so it generally shares it in a covalent bond. This element needs four electrons to be stable, so it can form single (such as the bond with hydrogen), double (such as the bond with oxygen) or triple bonds (such as the bond with nitrogen).
It can also form bonds with other carbon, and they can form longs chains, that's why there are a lot of organic compounds (the compounds with carbon). Carbon can form rings too, such as in benzene.
Out of the three you gave ecosystem is what I would call the most broad. An ecosystem includes living AND non-living things in an area
Community is all the LIVING things in an area (plants are included and I think bacteria is too, but I'm not sure)
Population is pretty narrow it just looks at specific species in one area. Population of mosquitoes doesn't include butterflies, if only looks at mosquitoes
Hope this helped!
Answer : Unit of any measurement can be defined as a definite magnitude of a given quantity, which is defined and adopted by convention or by law, that is widely used as a standard for measurement of the same kind of quantity. If the unit system was not given to the measurements we would haphazardly complicate the calculations.
Example : If someone wrote 500 in the paper as a answer to a question. But forgot to mention the units of the measurements. It can be misinterpreted by anyone as there are no units written besides the number (unit less). Complications grow. One cannot simply predict is it 500 m? 500 g? 500 mL? 500 km? 500 s? or 500 M? anything can be guessed. To be specific about the answer to any problem we should always use units. Which will help to narrow down the approach of any problem and give a measurable related quantity about the associated problem.
I would say is b. The answer
