Answer:
<u><em>The answer is</em></u>:<em><u> </u></em><u>Many are associated in pairs, trios, groups or clusters, and their distribution in filamentary structures.</u>
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Explanation:
<em>Galaxies rarely appear isolated and their distribution in the Universe is not uniform</em>. Many are associated in pairs, trios, groups of some tens or clusters of up to a few thousand. <em>These groups are held together by gravitation.
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The large-scale distribution of galaxies seems to indicate that they are concentrated along large filamentary structures.
<u><em>The answer is</em></u>:<em><u> </u></em><u>Many are associated in pairs, trios, groups or clusters, and their distribution in filamentary structures.</u>