Why is the Audi A4 hybrid battery located under the trunk floor?

I noticed in photos of the Audi A4 hybrid that the battery is located under the trunk floor, while other hybrid models have the battery in the trunk. Is there a specific reason for this placement?

The Audi A4 hybrid battery is located under the trunk floor for safety reasons. By placing the battery below the trunk, it helps to lower the car's center of gravity and improve handling in the event of a collision.