Lateral is Latin term which means side. It is mostly used to describe sides of an object, so we can say for example side of the box, side of a car, side of a human body... Since -equi- mean <em>equal</em> and lateral means <em>side</em>, the correct answer is D, the object , or in this case a box whose sides are all equal.
Potentially confusing answer could be C (having more sides). As a synonym for this we would use another Latin prefix <em>multi-</em> which means <em>many </em>(multilateral)