I can only see 1 answer that says 50%?
So it's 25%?
However, if the answers are related to the chance of getting this question correct then it becomes a mathematical paradox.
I believe this is basically it - there are 4 possible choices so it should be 25%, but as there are two 25% choices it's 50%, but then there is only 1 50% option, so it's 25%.... and so on.