Final answer:
The substance that will form a solution when mixed with solid sodium chloride is methanol (CH₃OH).
Step-by-step explanation:
When solid sodium chloride (NaCl) is mixed with a substance, it will form a solution if the substance is capable of dissolving the NaCl. Among the options given, the correct substance that will form a solution with NaCl is option b) CH₃OH(l), which is methanol. Methanol is a polar solvent that can dissolve polar compounds like NaCl.