The IR spectrum of a solid can be taken by dissolving it to create a solution. An appropriate solvent is Choose... because its IR stretches are

An appropriate solvent is only in the fingerprint region.

Explanation:

For scientists to study the infrared spectra of substances in the various states of matter, solutions are usually made with solvents. However, it has been noted that some of these solvents can interfere with the reaction spectra or be absorbed within the range of the solutes. A solution to this problem is using the right solvents with non-interfering infrared spectrum and which have no chemical effect on the solute.

The bands formed by the solvent should also be located in the the fingerprint spectrum. Examples of solvents used to achieve this and which meet up these requirements include, Carbon tetrafluoride and Carbon disulfide.  

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

the electrical  conductivity  of asolution  of an electrolyte is measured by determining the resistance of thesolution  between two flat or cylindrical electrodes separated by a fixed distance.