Question

A scientific _______ is a principle that describes the behavior of a natural phenomenon. A. Model. B. law. C. theory d. Analysis

Answer 1

A scientific law is a principle that describes the behavior of a natural phenomenon. 

Example:  Newton's Laws of Motion

Answer 2

Hello there!

A scientific _______ is a principle that describes the behavior of a natural phenomenon.

A scientific law is a principle that describes the behavior of a natural phenomenon.

Therefore, 
Your answer is Law.
B. law