With the frequent occurrence of smog weather in Beijing at the end of last year, people pay more and more attention to air quality. (1) PM 2.5 refers to the atmospheric median diameter.

(1)PM2.5 refers to particles with a diameter less than or equal to 2.5 microns in the atmosphere, also known as particles that can enter the lungs. It can be known that controlling PM2.5 is to reduce the emission of inhalable particles. (1) the city to increase the roof greening? ② Strengthen dust control at construction sites and roads? ③ Develop urban rail transit and bus rapid transit? Severe investigation and punishment of burning garbage and straw can reduce the emission of inhalable particles, so the answer is D.

(2) According to the algebraic sum of positive and negative valence in the compound is zero, the valence of sulfur in SO2 can be obtained as follows: x+(-2)×2=0, and the solution x =+4;

So choose B.

(3)① Fossil fuels include coal, oil and natural gas.

So the answer is: natural gas.

(2) According to the meaning of the question, the solution of absorbing carbon dioxide in the capture chamber is sodium hydroxide solution, and the sodium hydroxide solution can be generated by adding calcium oxide and Y solution in the separation chamber; Calcium oxide can react with water to generate calcium hydroxide, while calcium hydroxide can react with sodium carbonate solution to generate sodium hydroxide solution and calcium carbonate precipitation; Therefore, the reaction in the reaction separation chamber is the reaction of quicklime with water, calcium hydroxide and sodium carbonate;

So the answer is: Cao+H2O = Ca (OH) 2; ca(OH)2+na2co 3 = CaCO 3↓+2 NaOH。

③ Because calcium carbonate generates calcium oxide and carbon dioxide at high temperature, the added A can be calcium oxide, so calcium oxide can be recycled.

So the answer is: NaOH ..