Explanation:

- The sentence talks about addressing the issue of crowded public spaces due to the coronavirus. The aim is to modify or improve these areas.

- Option 1: Conserve - This means to protect or preserve something as it is. It doesn't fit well since conserving wouldn't help with congestion.

- Option 2: Congest - This means to overcrowd or block. Since the issue is congestion, adding more isn’t the solution.

- Option 3: Cooperate - This means to work together. While relevant in pandemic contexts, it doesn't directly address physical spaces.

- Option 4: Rehabilitate - This means to restore to good condition. It’s more about repair, less about redesigning for better flow.

- Option 5: Redesign - This means to plan something anew or modify the design, making it a perfect fit for relieving congestion by altering layouts.