Step 1: Define personality.
Personality refers to an individual’s unique patterns of thoughts, emotions, and behavior that are influenced by social and cultural context.
Step 2: Relationship with culture.
Culture provides values, norms, and shared experiences that shape the subjective aspect of personality, influencing identity, preferences, and behaviors.
Step 3: Conclude.
\[
\boxed{\text{Culture (Option A) is the source of personality's subjective aspect.}}
\]