1. Principle of electrolytic refining

In electrolytic purification of a metal:

• Anode = impure metal
• Cathode = pure metal sheet of the same metal
• Electrolyte contains a soluble salt of that metal.

For copper purification:

• Impure copper dissolves at the anode: $\mathrm{Cu \rightarrow Cu^{2+} + 2e^-}$
• Pure copper is deposited at the cathode: $\mathrm{Cu^{2+} + 2e^- \rightarrow Cu}$

2. Apply to the given case

The sample is copper containing zinc impurity. Since we want to purify copper, the setup must be:

• Anode = impure sample of copper
• Cathode = pure copper

3. Check the options

• A: cathode = pure zinc, anode = pure copper
  Wrong, because cathode should be pure copper, not zinc.

• B: cathode = impure sample, anode = pure copper
  Wrong, because in refining the impure metal is made anode, not cathode.

• C: cathode = impure zinc, anode = impure sample
  Wrong, because cathode should be pure copper.

• D: cathode = pure copper, anode = impure sample
  Correct. This matches the standard electrolytic refining arrangement.

4. Final answer

Therefore, the appropriate electrodes are: $\boxed{\text{cathode = pure copper, anode = impure sample}}$ So, Option D is correct.