<span>"Hypothesis, because tentative means unsure."
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The difference between analog and digital signals is that an analog signal is a continuous electrical message while digital is a series of values that represent information. Analog is conveyed by electrical current variations.
Answer : Option D) Fewer people have skin pigmentation lighter than the central peak than people who have pigmentation darker than the central peak.
Explanation : The quantitative variation which is shown for the skin is best explained by option D. Which shows that fewer people have got skin pigmentation which is lighter than the central peak in the graph, compared to the people who have darker pigmentation than the central peak.
The *heart* is the main organ of the circulatory system.
The circulatory system consists of three independent systems that work together: the heart (cardiovascular), lungs (pulmonary), and arteries, veins, coronary and portal vessels (systemic). The system is responsible for the flow of blood, nutrients, oxygen and other gases, and as well as hormones to and from cells.
From lowest to highest hierarchy it would be: planet, star, solar system, galaxy.
