The length of a football field is 120 yd. the width of the football field is 50 yd. which is the correct unit of measurement to use when figuring out how much rope is needed to surround the field?
a. yd
b. yd squared
c. yd cubed

The answer is:  [A]:  "yd" .

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.