Why would you write that you were required to file? If you weren't in Canada at all in 2010, then it's unlikely you needed to file that year. You need to answer two questions for yourself.
First, were you a tax resident of Canada in 2010 despite being outside the country for most or all of the year? Look here to answer that question: http://www.cra-arc.gc.ca/tx/nnrsdnts/cmmn/rsdncy-eng.html Even if you find that the answer is yes, the answer might still be no if you consider the effect of a tax treaty Canada might have with the country you were in.
Second, if you were a non-resident of Canada, did you have any income connected with Canada that would have forced you to file a return? Did you sell any property in Canada? http://www.cra-arc.gc.ca/tx/nnrsdnts/ndvdls/nnrs-eng.html
So if I apply say July 30 this month, is the application asking for up until July 30 2010? Because I left Canada in March 2010 so am I allowed to put that I was t required to file taxes for 2010? Technically I would have had to file for January and February of 2010 because I resided in Canada.
Most likely, the answer to all of these questions is no. In that case, you can tick the box saying you weren't required to file with a clear conscience.