What happens if an exchange cannot be completed?

When dealing with exchanges in Magic: The Gathering, if an exchange cannot be completed, it is important to understand what this implies. The concept of an exchange generally involves two parties or elements that attempt to transfer something from one to the other, such as effects, permanents, or resources.

If for some reason an exchange cannot be completed, it means that the conditions to successfully complete the exchange have not been met. For example, if one player attempts to sacrifice a creature but cannot because the creature has left the battlefield, the exchange cannot proceed as planned. Consequently, in such situations, no part of the exchange occurs—meaning that no resources or effects change hands. This is in alignment with the rules of the game, which state that if an exchange cannot be completed for any reason, the intended actions do not trigger or resolve.

The other options suggest different outcomes that do not match this principle. Some imply actions might still occur despite the exchange failing, while others suggest reverting to a previous state, which is not how exchanges function in this context. Thus, understanding that a failed exchange results in no actions occurring is crucial for interpreting game mechanics correctly.