The answers are
1. C
2. A
3. B
I believe the answer is: theory
Theory refers to the initial ideas that is used as an explanation for a certain principle.
Even though technically theory is just a form of guess that initiated before making the experiments, the guess is based on the general principles that accepted by most people in that field and could be changed depending on the available evidence.
“Lost Colony” is one theory of Roanoke that has continued over the centuries, but no one has come up with a satisfactory answer.
