The answer to the original question is that the 2 vehicles currently on fleet that Hertz class as Group D are the latest Chevrolet Cruze and the VW Jetta.

Both are 4 door sedans. Both were formerly Group C cars, but as they have got bigger they have now gone up a grade. Prior to this, Group D (and they had few of them) cars were the Nissan Altima Coupe, but that model is no longer produced. V6 Muatang Coupes were also in this Group, but they have not had these since the change to the current model type.