The most relevant detail would be "there is so much to do".
To determine which detail would be most relevant to the central idea that "summer is the most fun season because there is so much to do," we need to consider the options in relation to the central idea. Among the given options, the detail that highlights the wide range of activities available in summer would be the most relevant. Therefore, the correct answer would be a detail that emphasizes the abundance of things to do during the summer season.
