Detailed Instructions: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Problem: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 C. <4> Heat the sample between 400 and 700 C. <5> Heat the sample in 0.1 M hydrochloric acid.
Solution:
4