When overriding standard buttons in Salesforce Classic and Lightning Experience, different technologies are used.
Salesforce Classic:
Visualforce pages are used to override standard buttons like Edit.
Lightning Experience:
Lightning Components (Aura Components or Lightning Web Components) are used.
Option C: A Visualforce page in Salesforce Classic and a Lightning component in Lightning Experience Correct Answer.
In Salesforce Classic, override the Edit button with a Visualforce page.
In Lightning Experience, use a Lightning Component to override the Edit action.
Reference:
Overriding Standard Buttons
Overrides in Lightning Experience
Options Not Applicable:
Option A and B: Lightning components cannot be used in Salesforce Classic.
Option D: A Lightning page cannot be used to override standard buttons.
Conclusion:
The developer should use a Visualforce page in Salesforce Classic and a Lightning component in Lightning Experience, which is Option C.