Answer:
Option B. compounds
Explanation:
Compound is a type pure substance which is formed when two or more than two elements combine together chemically in a fixed ratio. It is represented by a chemical formula. Chemically combine means the elements present in the compound make bonds in order to hold each other. So they are not separated by physical methods. It is separated from one another by chemical methods.
Earths place.
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Mercury, Venus, Earth, Mars, Jupiter. Saturn, Uranus, Neptune
The earth is the third planet from the sun.
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Natural selection act directly upon <u>Alleles</u>
Explanation:
Genes, such as that of fur color, have many variants called alleles. Natural selection act on the alleles and chooses the best fit for an environment and eliminates the disadvantageous ones from the population over generations. Mutations are a rare occurrence that increases the number of allelic variants of a genes on which natural selection can act upon.
Ecosystems can be large and are made of biomes. Some examples of ecosystems are deserts and forests.