chem ce mc

I think you have got the wrong answer. The answer should be (2) only.

A separating funnel is used for the separation of two immiscible liquids. In other words, a separating funnel should not be used if the two liquids are miscible.

(1) is incorrect. Both of the two solutions are aqueous, using water as the solvent. The two aqueous solutions must be immiscible and thus they cannot be separated by using a separating funnel.

(2) is correct. Water and octane are immiscible. Therefore, the aqueous NaCl solution and octane are separated into two layers, and the two layers can be separately by using a separating funnel.

(3) is incorrect. Ethanol and octane are partially miscible. Therefore, the two liquids cannot be separately by using a separating funnel.