Task: Question Answering
Input (English): Question: For the analysis of traces of inorganic constituents, in samples of organic nature, a preliminary treatment of the sample is needed, which normally consists of: 
 Options:  <1> Dissolve the sample in cold water. <2> Dissolve the sample in hot water. <3> Dissolve the sample between 30 and 70 ºC. <4> Heat the sample between 400 and 700 ºC. <5> Heat the sample in 0.1 M hydrochloric acid.
Output (English): 4