The answer is a) trait.
Trait theories focus on identifying and measuring the specific traits that make up human personality. These theories suggest that personality can be understood by examining a small number of fundamental traits that influence behavior across different situations. For instance, the Five Factor Model, which includes traits such as openness, conscientiousness, extraversion, agreeableness, and neuroticism, is one of the most well-known trait theories. Unlike psychodynamic, behaviorist, or humanistic theories, which may emphasize different aspects of human psychology or behavior, trait theories provide a more straightforward and quantifiable approach to understanding personality.