What does a scientist use to explain a set of observations

A)  introspection
B)  a theory 
C)  common sense
D)  empiricism

Introspection

The examination of one's own thoughts and feelings, a reflective process focused on understanding one's inner experiences.

Empiricism

The philosophy that knowledge comes primarily from sensory experience, emphasizing the role of observation and experimentation in science.

Theory

A systematic set of principles or explanation for understanding, predicting, or controlling some aspect of the natural or social world.