Analysis of test questions: according to the working principle of the device, the role of electrode A is to adsorb negatively charged pulverized coal, so it should be connected to the positive pole of power supply, where A is correct and B is wrong; The process of flue gas purification is to enter from C first, and the electrons generated after the air is ionized by the strong electric field near the wire E are captured by the pulverized coal, and the negatively charged pulverized coal is adsorbed on the positively charged metal tube when passing through the chimney, so C is correct and D is wrong.