Step 1: Concept
An ideal solution is a solution in which the interaction between the molecules of the components does not differ from the interactions between the molecules of each component.
Step 2: Meaning
For such solutions, the partial vapor pressure of each component is proportional to its mole fraction.
Step 3: Analysis
Henry's law applies to dilute solutions of gases in liquids. Raoult's law ($P_{i} = X_{i}P_{i}^{\circ}$) defines the behavior of an ideal solution across all concentrations.
Step 4: Conclusion
Compliance with Raoult's law is the defining characteristic of an ideal solution.
Final Answer: (A)