Key idea: Separation techniques for solid mixture

Steps:

• Identify components: Copper powder (insoluble solid) and sodium chloride (soluble salt).
• Dissolve NaCl in water to form solution, leaving Cu powder as residue.
• Filter mixture to separate Cu powder (residue) from NaCl solution (filtrate).
• Evaporate filtrate to recover pure NaCl solid.
• Dry Cu powder if needed for purity.

Why C is correct:

• C (1, 3, 4) matches dissolution, filtration, and evaporation/drying, standard for insoluble solid and soluble salt per separation principles.

Why the others are wrong:

• A includes irrelevant method 2 (e.g., sieving, ineffective for fine powders).
• B omits key steps 3 and 4 (filtration and recovery).
• D excludes essential dissolution (1), preventing separation.

Not enough information on exact methods 1–4, but C fits typical process.

Final answer: C