According to the meaning of the question, this question needs to verify sulfur dioxide first, then carbon dioxide, and put magenta solution in device B to verify sulfur dioxide first; Because sulfur dioxide can also react with limewater to produce precipitation, which will interfere with the verification of carbon dioxide, it is necessary to ensure that sulfur dioxide is removed before the verification of carbon dioxide. Therefore, it is necessary to add acidic potassium permanganate solution to device C.

So the answer: (1) clarify limewater.

(2) The magenta solution in B faded

(3) Ethyl methyl ester absorbs sulfur dioxide with saturated sodium bicarbonate solution and generates carbon dioxide at the same time, which interferes with the inspection of carbon dioxide.