c - Combined fuel economy
Combined fuel economy - To get this figure, a car's official fuel consumption during town driving and out (known as urban and extra urban, respectively) is added together and divided by two to give an average figure.
This is the most frequently quoted economy figure because it best reflects the sort of driving most people do. If you only drive in town, it's likely you will not achieve as good a consumption, while if you drive mostly on the motorway at a steady speed you will probably better the combined figure.
Fuel Economy Challenge