Step 1: Concept
Identifying a word that fits the positive context of research supporting a theory.
Step 2: Analysis
- Corroborated: Confirmed or gave support to a statement or theory.
- Contradicted: Denied the truth by asserting the opposite.
- Weakened: Made less strong or reliable.
- Rejected: Dismissed as inadequate or inappropriate.
Step 3: Conclusion
"Extensive research" generally serves to support or confirm a theory, making "Corroborated" the most suitable choice.
Final Answer: (1)