Being still in school, I can vouch that there are typos and grammar errors throughout. A few of my teachers are not native English speakers and their writing definitely make the easy to see. No matter how good the editors, books will have typos. It's just not a big deal.
--Sent From My Galaxy S4
You are looking at it through the eyes of an adult. Put yourself in the mind of a 9 year old. He wants to do well in school. He wants to please his parents and teachers. He wants to show pride in his work. He's trying hard at test day! And he knows the answer by deducing the problem the way his thought process was conditioned, but the answer is not there! Oops! Someone forgot to put it in the sheet. Oh no big deal! Happens all the time! Right?
Kid circles WRONG answer because he doesn't understand the mistake made by the adults! He needs to write a choice. Awkward!