Quantity A is greater will translate in laymen’s terms to “A is always greater than B”
Same with “B is always greater than A”
Or “A and B are always equal”
Because we can show a case where A is greater than B (x=-6) and a case where they are equal (x=0), then their case is always true.
When there are two or more cases that we can demonstrate to be true, then we cannot determine “always” so the answer must be D.