<span>Sand dunes can encroach on human habitats. Sand dunes move through a few different means, all of them assisted by wind. One way that dunes can move is through saltation, where sand particles skip along the ground like a rock thrown across a pond might skip across the water's surface. When these skipping particles land, they may knock into other particles and cause them to skip as well. With slightly stronger winds, particles collide in mid-air, causing sheet flows. In a major dust storm, dunes may move tens of meters through such sheet flows. And like snow, sand avalanches, falling down the steep slopes of the dunes that face away from the winds, also moving the dunes forward.
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Answer:
Tubman decided to help the Union Army because she wanted freedom for all of the people who were forced into slavery, not just the few she could help on the Underground Railroad. And she convinced many other brave African Americans to join her as spies—even at the risk of being hanged if they were caught.
Your answer would be A (having fingerprints recorded).
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