If the correct answer is duplicated, then I think that's grounds for investigation of a possible duplicate question, not a definitive sentence of duplication.
We've had some similar points of discussion from here on Meta Stack Overflowhere on Meta Stack Overflow, which in itself was cited on Gaming for "Should different questions that yield similar/duplicate answers be closed?". To quote from the Meta question,
If you ask a question similar to another question and it is likely to get the exact same answer, you have yourself a duplicate question.
Now, the key thing here is that there's two components here - getting the same answer and being similar. The presence of one is often a clue to check for the other - so if the answer to one question is the same as an existing one, that's a clue to check for if it might be a duplicate.
But there exist several cases where two questions can attract the same answer without being duplicates. It all boils down to the second point, that they have to be similar. If the differences are superficial, then it makes sense to close them. But here are examples of when things might attract the same answer but it would be rather callous to call them duplicates.
Kaestur Hakarl's answer to the Gaming question supplies 3 examples of situations where the answer to two or more questions are the same on a basic level, yet the questions are completely different. Sometimes a particular operation works as a solution to multiple problems - that doesn't make all those problems the same. Otherwise, "A large enough explosion" would be an answer that'd create a lot of duplicates for what it can solve.
Consider the situation where someone asks "Does variable
B
affect algorithmA
?", and an answerer goes out of the way to make an excellent answer that describes the full of what affects algorithmA
. This answers the given problem, but it also answers the question of "How does algorithmA
work?", which has not yet been asked. When the latter question gets asked, it seems very awkward to close it as a duplicate of the former - who looking for general info on algorithmA
would think to find their answer in a question that's focused on variableB
?