Multiple Choice Probability Puzzle - an analysis

If you assume the problem is correct, in other words one and only one of the four answers is correct, then you have to exclude the two identical answers (25%). You are left with 50% and 60%. You pick one of them at random, and the chance to be correct is 50%.

If you start with the assumption that the problem is wrong, then ... it's wrong.

I see that despite getting 3 upvotes in a matter of minutes, this item is now ranked down in the mid 400s. Clearly it's been flagged.

Would someone please explain why this is sufficiently inappropriate to deserve getting flagged? I just want to know so I can avoid submitting the wrong kind of items.

Thanks.