Final answer:
During World War I, front-line trenches were protected by barbed wire entanglements and sandbags.
Step-by-step explanation:
During World War I, the front-line trenches were protected by various defensive measures. One of the main forms of protection was barbed wire entanglements placed in front of the trenches. This wire was designed to slow down and trap enemy soldiers, making them vulnerable to artillery fire from the defenders. In addition to barbed wire, sandbags were stacked along the top of the trenches to provide additional cover and protection from gunfire and shrapnel.
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