B.   You chose the number 584.

While the answer key authoritatively points to a different answer, we’re going to give you credit anyway. One way to come to the conclusion that 584 does not belong is to add the digits in the one’s and ten’s place and compare this sum to the digit in the hundred’s place. Say what? Again, by following the above process, you’ll find that for each number, there is a difference of “1” except in the case of 584 where the difference is “7.” One of my students supported his choice of this answer in the above way, and I gave him credit.