In daily life, the following practices are correct: If you find a gas leak in your kitchen, you can

A. The mixture of flammable gas and air or oxygen may explode in case of open flame, static electricity, electric spark or heating, and electric sparks will be generated when the exhaust fan is opened, so it is wrong

B. The density of carbon dioxide is greater than that of air, it will gather in low-lying places, there is more carbon dioxide in the cave, carbon dioxide can not supply breathing, and the amount exceeding the normal value will suffocate people to death, so it is correct

C. The main component of coal gas is carbon monoxide, which is difficult to dissolve in water, and putting a pot of water on the coal stove can not prevent gas poisoning, so it is wrong

D. Moldy rice contains toxic aflatoxin, which is not easy to be destroyed and cannot be eaten under general heating conditions, so it is wrong

So choose B

A. Coal gas is flammable, and the gas mixed with air is prone to explosion when exposed to open flame, static electricity, electric spark or heating, and the power switch of the exhaust fan will be turned on immediately to produce electric sparks, which may explode, so this measure is wrong

B. When entering a karst cave where the gas is not smooth, you can use a torch to do a light test, and you can't use a flashlight, so the option is wrong

C. When the oil pan catches fire, extinguish it with a lid, using the reaction principle of isolating oxygen, so the option is correct

D. Because carbon monoxide is insoluble in water and does not react with water, putting a pot of water on the coal stove cannot prevent gas poisoning, so the option is wrong

Therefore, C

a. The treatment method of gas leakage is to close the valve first, then open the doors and windows for ventilation, and cannot use electricity (turn on the ventilation fan, turn on the light), etc., so A is wrong;

B. Gas poisoning, drinking a lot of milk is not effective, and the patient should be put in a ventilated place and then artificial respiration, so B is wrong;

c. Hard water contains a lot of calcium and magnesium compounds, and it is not easy to wash off the stolen goods when washing clothes, so it is best to convert it into soft water by boiling and then washing clothes, so C is wrong;

D. Garbage can be converted into resources through classification and recycling, which is the best way to deal with garbage, which does not pollute the environment, but also saves resources by recycling, so D is correct

Therefore, choose D