Task: Question Answering
Input (English): Question: The voltammetric methods of anodic redissolution: 
 Options:  <1> They are based on the preconcentration of analytes on the surface of an electrode and are characterized by their low sensitivity, since the surface of the electrode is very small. <2> They apply exclusively to the determination of traces of metals by oxidation on a mercury electrode. <3> They require the application of a stage of accumulation and another of redisolution in which intensity-time curves are recorded. <4> They are used for the determination of metals that, once deposited, are oxidized electrochemically. <5> They are based on the variation of the potential that the working electrode experiences as the deposited substance is redissolved.
Output (English): 4