When can a player activate an ability in a game?

A player can activate an ability when they have priority. In Magic: The Gathering, priority is a key concept that determines when players can take actions, including activating abilities, casting spells, or playing lands. When it is a player’s turn to act and they have priority, they can choose to activate abilities as long as the rules and conditions for those abilities are met.

For example, after a spell resolves or an ability completes, the active player typically gains priority first, allowing them to activate abilities. If they choose not to take any actions, priority passes to the next player, who can then also activate abilities or take other actions if they have priority.

This understanding is essential because it emphasizes that a player can activate abilities not only during their own turn but also during other players' turns, provided they have priority at that moment. It opens up strategic interactions in the game, such as responding to opponents’ actions or utilizing abilities during crucial parts of gameplay.

Other options suggest limitations that do not align with the game's rules. For instance, stating that a player may only activate an ability during their turn overlooks the dynamics of priority and the ability to respond to spells or effects during any player's turn. Thus, the correct answer highlights an essential part of the game