It depends on what the graph shows. I need to see the graph to help you. sorry
When we say "closed under addition" in the context of rational numbers, we mean to say that when we add up rational numbers then, the sum is also a rational number.
From the given choices above, the one that should the characteristic of being "closed under addition" is only fourth equation. Both 1/2 and 0.5 are rational numbers. On the other hand, 1 is also a rational number.
The answer is E.4
The equation is:
Since
, then
Therefore, the equation is:
⇒
