Final answer:
When a mixture of compounds is treated with aqueous NaOH, only the acidic compound will remain in the organic phase.
Step-by-step explanation:
If a mixture of compounds is treated with aqueous NaOH, the acidic compound will react with the base to form a salt and water. In this case, compound a is acidic, so it will react with NaOH. Compound b is basic, and compound n is nonacidic. Since basic compounds do not react with NaOH, only compound a will remain in the organic phase after treatment with aqueous NaOH. Therefore, the correct answer is option 1) a only.