Professor Zhang: During the economic depression in the West, the air pollution caused by car exhaust will be greatly improved, because the number of people driving to work will be greatly reduced  Engineer Li: I'm afraid this is not the case  The number of people buying new cars during the recession was greatly reduced
The older the car, the heavier the pollution caused by excessive exhaust emissions
Putting forward a consideration, although it does not deny Professor Zhang's argument, it can weaken the support of this argument to his conclusion