Which response indicates agreement about the game being boring?

The correct response indicating agreement about the game being boring should reflect an acknowledgment of the sentiment expressed. In this context, the choice that confirms the idea of agreement about the game being boring aligns with a plural subject. "Did they" implies that the speaker is referring to a group that shares the same opinion about the game’s lack of excitement, effectively agreeing with the premise.

In this scenario, the other choices do not directly endorse the sentiment of boredom. The other options focus on singular subjects or questions that do not explicitly affirm an opinion about the game. Therefore, the response that best communicates agreement among a group is the one that speaks to collective sentiment, making "Did they" the most fitting choice in this context.