Can you guess the word if you are not 100% sure what was spoken?
Deduction means to use the given information and reach to a certain conclusion.
So, (A) Yes, the word can be guessed even if we are not 100% sure what was spoken.
In English, the words which are used to indicate this certainty, probability or deduction are modal verbs.
And when we are not 100% sure then we can use modal verbs such as-should, might, may or could.