Question

which of the following best illustrates why a scientific theory might be modified?
the public does not believe the theory
a single scientist disagrees with the theory
the theory has been in place for over 50 years
new experimental data provides new understanding

Explanation:

A scientific theory is based on evidence. Public opinion, a single scientist's dissent, or the theory's age (like 50 years) don't change it. New experimental data, which is evidence - based, can provide new understanding and lead to a theory's modification.

Answer:

New experimental data provides new understanding.