Which phrase suggests that the girl is reminiscing about a past game?

The phrase "Didn't they" effectively suggests that the girl is reminiscing about a past game because it implies that she is reflecting on something that happened previously. This particular construction indicates that she is recalling an event or action, particularly in the context of a game. The use of the past tense "didn't" signals that the girl is looking back to a time when certain events took place, making it clear that her thoughts are anchored in nostalgia or reflection on past experiences.

In contrast, the other phrases—"Weren't they," "Couldn't they," and "Shouldn't they"—are not as clearly indicative of a nostalgic sentiment. While they each pose questions about hypothetical situations or past conditions, they do not evoke the same sense of memory or past participation as the chosen phrase. "Weren't they" suggests a consideration of previous conditions or characteristics rather than a direct reminiscence. "Couldn't they" is focused on possibilities that may not have happened, and "Shouldn't they" addresses expectations rather than actual experiences. Therefore, the phrase "Didn't they" stands out as the most suitable choice for expressing reminiscence about a past game.