freeiqtest.info question - what number should replace the question mark?

I took an online IQ test(http://www.freeiqtest.info) and encountered this question:

I could not find out any valid pattern that determined what number is in the third section of the pie chart(the one that is represented with the question mark). The only patterns I found were very arbitrary, some of which I would not even call patterns. The only sort of non-arbitrary pattern I found was that if the first number in the pie chart is even, then the third number would also be even, and it also goes for odd numbers. However, there are two even numbers in the options given. The only pattern I found(which is quite vague and unclear) that could possibly give an answer to this problem would be the fact that the third number in each pie chart is a one-digit number, so the answer is 8. However, I really want to know the real pattern behind this puzzle. Any help in this puzzle is appreciated. Thank you.