Subject: the acceleration mystery

I am a middle school math teacher who is currently giving the SAT's to 
my students.  After the science portion of the exam, I had a student 
come up to me and ask me about one particular question (notice I wrote 
AFTER the test for all of those undercover SAT special agents out 
there..).  I would like to explain the question and the correct 
response with my students.
     The question showed a graph of a car starting at 0 mph, gaining 
speed to 60 mph and hold steady at 60 mph for 2 minutes and then slow 
down to a complete stop.  Naturally, the car was in a state of 
non-acceleration when it was at a constant speed of 60 mph, but I 
wanted to be able to explain to my students why that was the correct 
response.  I remember in a college physics class that acceleration was 
basically a change in velocity, whether you are speeding up or slowing 
down.  Am I remembering right?

Re: the acceleration mystery