Deionized water is water with which of the following removed?

The story behind the answer

Deionized water is water that has had its dissolved ions removed; among the choices, iron fits because it exists in water as charged ions (Fe2+/Fe3+) that ion-exchange resins specifically capture. Oxygen and hydrogen are the elements that make up H2O itself, and “uncharged atoms” aren’t what deionization targets.

Why it matters: Ions make