Teenagers should （encourage） to solve their problems by themselves．
Tom has invented a tree﹣planting machine．
I think no one is （create） than him．He's a boy full of strange ideas．
根据句意，用所给单词的适当形式填空．
If you want to make yourself （understand），you'd better speak clearly and slowly．
Sandy's grandparents （marry） for 50 years．
（luck），the man hurt badly in the accident．