Range

Bob Lochel writes:

“I used this question as part of a benchmark assessment given to over 1,100 students at our high school, as preparation for the state test.  Only 14% of students gave the correct answer B, while 66% of students chose A as their response.  I’m not surprised that students would perform weakly on a domain/range question, but I am surprised that so many chose A.  I featured this problem as a set-up for a domain and range activity on my blog: http://mathcoachblog.wordpress.com/2013/01/22/home-on-the-range-and-the-domain/, but feel free to share it with the mathmistakes crowd.”

So, what do we think about choosing A? Any theories?