This question is impossible to answer. The answer isn't even 0% because that in itself is an incorrect answer. Let's look at the options:
Realistically, you'd have a 1 in 5 chance of answering a five-choice question correctly. So the answer would be 20%. But the problem is that there are two answers of 20%. That makes the answer 2 out of five answers. That means, based on random chance, you'd have a 40% chance of just guessing it. But, since that'd mean there'd only be a 1 out of 5 answer, it brings it back to 20%. That creates an infinite loop. This should mean the answer would be 0%. But, since that in itself is an option, it means that there would actually be a 20% chance of getting it right. Which means the question is insolveable.
Now, if the answer can only be a single letter and one of the five must be considered correct, that changes things slightly. The answer would have to be a single letter. That means that you have a 20% chance to get it right. This causes the chance of getting the right option to become 50% if you know what's going on. That makes every option wrong by extension. But in the end, you'll still have a 20% chance of getting it right. It just means that the answer you choose can't be absolutely right because the question itself is wrong.