Lowest Common Denominator refers to lowes t common multiple. These expressions have two terms 'x' and 'y' and we want to choose the expression that has the highest power such that the other expressions can be multiplied into the common denominator.
For the 'x' term, the highest power is x⁴ and for the 'y' term, the highest power is y⁵
Common denominator of A, B, C, and D: x⁴y⁵