Answer:
C. executive
D. life
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Explanation:

The United States have represented form of democracy.
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Answer:
European explorers unwittingly brought with them chickenpox, measles, mumps, and smallpox, decimating some populations and wholly destroying others.
Explanation:
Answer:
expectancy effects
Explanation:
Expectancy effects: In psychology or scientific research, the term "expectancy effect" is described as a type of reactivity that generally occurs when a "research participants or subjects tend to expect a specific result and therefore they unconsciously influence or affects the outcome and hence report the result that is being expected.
In the question above, the given statement signifies the 'expectancy effects'.
a
The amount of energy at each trophic level decreases as it moves through an ecosystem. As little as 10 percent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat.