Answer:
<h2>Biking with friends.</h2>
Explanation:
Biking with friends is a recreational activity through which can be gathered many people, because each one can have a bike and just go on the road, enjoying that moment, having friends and family all together, no matter how many people, they can all ride a bike.
On the other hand, other options are not viable because those are activities that demand a lot of physical preparation (which makes it not recreational, like 5k and 10k races), and others, like swimming, cannot be set to be a community activity, it's too individual.
