Identify This: Four Production Audi Models

Since you seemed to have enjoyed the previous quiz with the classic Alfa Romeo models (see here), we thought we would come up with a new series of our own featuring a different automaker each week. For this puzzle, we chose the brand with the four rings from Ingolstadt, which is more commonly known as Audi. To help you out, we will give you a couple of hints. The first one is that all four vehicles you see pictured here are series production models, while the second clue is that each one is from a different decade. We will reveal the names and show full pictures of the four Audi production models in our next quiz. For now, you can leave your answers in the comments box after the break.