The use of idle biogas digesters should be

A, the main component of biogas can make methane, and it may explode when it is ignited or heated when it is impure, so it is wrong to do experiments with torches;

B, the composition of white vinegar is acetic acid, which can react with scale and can be used to remove scale in the pot, correct;

C, household appliances on fire, should first cut off the power supply, and then use dry powder fire extinguisher to put out the fire, correct;

D, "real gold is not afraid of fire" shows that the chemical properties of gold are inactive and correct;

So choose a.