If you have the software to do it, you can run the statistics to see if there is a good correlation between the answer given on that question and the overall score for the test. If the people who did better on the test in general got this question wrong, that question is probably not a good indicator as to which students know their stuff and which don't. If the people who scored well on the test as a whole did pretty well on that particular question, then that question is doing a good job of distinguishing between those who know the material and those who don't. (It might just be more difficult than the average question -- which might be something you want to keep. You want to have a few difficult -- but good -- questions on tests so that you can identify the A students from the C ones.)
If you don't have the software to run those item analysis statistics, you can do a little of that manually. Identify the top 5 or 10 student scores on the test ... and then see how they answered that particular question. That will give you a clue as to how the better students in the class perceived it. Sometimes, after considering all the possibilities ... I conclude that the question was good and legitimate, but just difficult. I try to have a least a couple of those on each test so that the best students will get better grades than those who didn't do the work.
I also look at whether or not the students chose the same "wrong" answer. Is there any legitimate reason as to why they chose it. Sometimes, they simply read/interpret a question differently from what I intended. If that's the case, then I didn't write it as well as I thought and I need to take some responsiblity for that.
Sometimes, I conclude that I didn't teach that content very well -- and I alter my teaching methods.
Other times, I conclude that lots of the students didn't study very much and didn't do "their part" in the learning process. In those cases, I am not afraid to let the bad grades stand so that students can learn a valuable lesson about the consequenses of not putting forth an effort to learn the material.
You might want to get a book (or find some good articles) on test construction and analysis. There is an art and science to constructing a good test and writing good test questions. It may be worth investing in a little continuing education for yourself in this area.