Answer:
A theory has to be revised in the event of a new scientific evidence discovery.
Step-by-step explanation:
This is because for an hypothesis to be passed to a theory, substantial scientific evidence has to be provided.
An existing theory, in the light of new found scientific evidence attached to it, has to be revised for the inclusion of the new found light.
The revision is done to update the theory as per the newly found light or to drop it if the newly found scientific evidence disapproves it.