Question

which is a characteristic of a scientific theory? well - tested non - modifiable a proven fact

Explanation:

A scientific theory is a well - substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. It is well - tested. A scientific theory is not non - modifiable as new evidence can lead to its modification, and it is not a proven fact (facts are individual observations, theories explain them). So the correct option is the one with "well - tested".

Answer:

well - tested