The answer is: [A]: "yd" .
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Note: Since we are referring to "how much rope is needed to surround the field" ; we are referring to the "perimeter"; or adding up the length of all the sides. So there will be no "squared units" (choice B — which would refer to the "area"; and no "cubic units" (choice C - would would refer to the volume of a 3-dimensional solid (e.g. rectangular prism; since we only have two dimensions {a football field; with only a length and width (no height) } ; and as mentioned; we are referring to the "perimeter"; which is the sum of the lengths of all sides.
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