Answer:
a cube that is 1 yard long, 1 yard wide, and 1 yard high
Explanation:
The dimensions for a unit cube are:
Please note that the units for each side MUST be the same (or if they're different, then the lengths have to be equivalent).
Looking at the answer choices, we can see that the last answer choice is a 1 yd by 1 yd by 1 yd cube, therefore it is a unit cube.