The weather in Beijing

A, afforestation can prevent wind and fix sand, reduce dust weather, which is feasible, so it does not meet the meaning of the question;

B, strengthening the management of urban construction sites and prohibiting the exposure of cement and sand can reduce dust, which is feasible, so it does not meet the meaning of the question;

C, the polluted air has nothing to do with dust, and it is impossible to prevent the air in the polluted area from flowing to Beijing, which is not feasible, so it conforms to the meaning of the question;

D, hardening rural roads and reducing dust on the ground can reduce dust, which is feasible, so it does not meet the meaning of the question.

So choose C.