Youknowthatballoonsm的精选

问题详情：Youknowthatballoonsmustbekeptawayfromsharpobjects.Theyalsoneededtobekeptawayfromflames.Afirecanweakentherubberandcauseittobreak.However,inthisexperimentyouwillfindouthowyoucanholdaballoondirec...