The word "Liberal" has several meanings, but a common one, especially in a non-political context, is related to giving or spending freely. A person with a liberal attitude is open-minded and not strict in the observance of traditional ways. When applied to giving, it means generous.
Let's analyze the options:
\[\begin{array}{rl} \bullet & \text{(A) Sober: Not affected by alcohol; serious and sensible.} \\ \bullet & \text{(B) Generous: Showing a readiness to give more of something, as money or time, than is strictly necessary or expected. This aligns with the meaning of 'liberal' in the sense of 'giving freely'. A 'liberal helping of food' is a 'generous helping'.} \\ \bullet & \text{(C) Reactionary: Opposing political or social progress or reform. (Antonym in a political sense).} \\ \bullet & \text{(D) Affectionate: Readily showing fondness or tenderness.} \\ \end{array}\]
The closest synonym among the choices is Generous.