Concept:
Solution types depend on physical states of solute and solvent.
Step 1: Check each option.
• (A) Sea water: Salt (solid) in water (liquid) $\rightarrow$ Correct
• (B) Brass: Solid in solid
• (C) Gasoline: Liquid in liquid
• (D) Iodine in air: Solid in gas
Step 2: Conclusion.
Thus, sea water fits condition.
Final Answer: Option (A)