Definition: In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.
Input: Article: Dear Earthmen ,  I have enjoyed my stay on your interesting unusual planet. I think I understand the life on earth now and I would like to give you my impressions. First of all you live in boxes. Every morning you leave your big boxes and get into smaller boxes on wheels. All these small boxes race around and around, and finally stop to rest. You then leave these boxes on wheels and go to very large tall boxes. After testing all days you get back in your little boxes and return to your big boxes. There you sit and stare at tiny glowing boxes with moving pictures on the front. Only one thing puzzles me. One day I went to a football game. A bunch of angry boys fought over a little round ball. Everyone yelled for them to stop but they kept on fighting. They were angry, I suppose, about being cooped up  in boxes all day. Thank you earthmen for this chance to get to know you.  Gratefully, The man from the Mars 
 Answer: boxes in which there are wheels
