Which statement describes a scientific theory?

A theory states how something behaves without explaining why.
A theory is a proven fact that cannot be changed.
A theory changes based on new observations and testing.
A theory is based on a single hypothesis or observation.

A theory changes based on new observations and testing.

Explanation:

Multiple observations and repeated trials results in the formulation of scientific theory.

The scientific theory is one of the methods used in science to explain a particular observation. They are usually ascertained from carrying out multiple trials and experiments to validate a claim.

A scientific theory simply provides an explanation into a phenomenon. A law just states how something behaves.

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)