Under what circumstances can something be "abandoned"?

A scheme card can only be abandoned during an Archenemy game if it is face-up and ongoing. This is because, in an Archenemy game, scheme cards represent the plans of the Archenemy, and their effects can significantly impact the game. Ongoing scheme cards are actively in play and can be interacted with, while other types of scheme cards might not fit the criteria for abandonment.

To abandon a scheme card properly, it must be one that is currently affecting the game in some way, which is why only face-up ongoing scheme cards are eligible for abandonment. This rule reinforces the notion of active game components that are available for player decisions, while disregarding cards that are not currently engaged in gameplay.

The other options do not correctly represent the rules concerning the abandonment of scheme cards. For instance, the ability to abandon any scheme card at any time does not align with the specific criteria established for ongoing scheme cards, indicating a misunderstanding of the distinctions between card types and their statuses in the game. Similarly, a scheme card cannot be considered for abandonment in a game state where players are still active, thus not aligning with the stipulation that there must be an ongoing aspect involved.