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:

Theories are very critical part of the scientific methods with usually starts with simple observations around.

Scientific theories abounds. They typically provide explanation into a phenomenon and gives us the reason why something occurs or not.

carla slowed down in the beginning of her trip, stopped, and then sped up

find the sum of the two horizontal vectors and the sum of the two vertical vectors

isoceles right angled triangle