Final answer:
The powers 0, 40, (-2), and 90 have in common that they are integers within the Real Number system.
Step-by-step explanation:
The powers 0, 40, (-2), and 90 have one thing in common: they all belong to the Real Number system. The Real Number system includes all rational and irrational numbers, and these powers fall within that category. Additionally, all four powers are integers. In mathematics, an integer is a whole number that can be either positive, negative, or zero. Therefore, the four powers have in common that they are integers within the Real Number system.