A)a new defensive tactic known as trench warfare
Trench warfare allowed the war to drag on for long periods of time because of the stalemates that ensue from the opposing armies refusing to give up the land under their controls, resulting in high casualties in no man's land.
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"Rust Belt" would be the best option from the list regarding a symbol of deindustrialization, since the term refers to the "rusting" of the old industrial plants.
The Constitution provides that an amendment may be proposed either by the Congress with a two-thirds majority vote in both the House of Representatives and the Senate or by a constitutional convention called for by two-thirds of the State legislatures.
