When a Scientific Paradigm Shifts,this Indicates That

Multiple Choice

When a scientific paradigm shifts,this indicates that:

A) scientists revert back to a previous paradigm.
B) the location of prestigious research has shifted from one nation to another.
C) scientists have come to a standstill on their discoveries of a particular topic.
D) scientific anomalies have amassed to a level that challenges the validity of an existing paradigm.