用括号内所给词的适当形式填空。
1. Our class play soccer for a week without _______ (stop).
2. It is one of the highest _______ (build) in this city.
3. Liu Yutian is the first person to walk the whole _______ (long) of the Great Wall.
4. I don't know how to make the problem much _______ (easy).
5. Every morning Jim is the _______ (early) student in his class.