What technology is used in the sport differential of the Audi A4?

I've heard about the sport differential in the Audi A4, but I'm not sure what technology it uses. Can anyone provide some insight?

The Audi A4's sport differential is an electromechanical system that can actively distribute torque to the rear wheels for better handling and cornering.

The Audi A4's sport differential utilizes a torque vectoring system that distributes power to the rear wheels individually, improving handling and traction.

The sport differential in the Audi A4 is a mechanical system that works with the car's stability control to distribute torque to the wheels with the most grip, increasing agility and stability.