Step 1: Approach
Recall which functional group reacts with Schiff's reagent.
Step 2: Recall
Schiff's reagent is colourless. Aldehydes react with it and bring back a magenta colour. Ketones, acids and ethers do not.
Step 3: Conclusion
The compound that gives the Schiff test is an aldehyde, option (C).
Final Answer:
Only aldehydes restore the pink colour of Schiff's reagent, option (C).
\[ \boxed{\text{Aldehydes}} \]