题目

阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。Litter is everywhere，doing great harm 【1】 the environment and life on our planet.Jeff Kirschner，who wants to build a litter-free world，started a global community named Litterati 【2】 (settle)this problem.The story began with his 6-year-old daughter.One day they were going on a hike when the girl noticed a 【3】 (break)plastic tub(浴盆)in a river.She said，“Daddy，that doesn’t go there.”That took Kirschner by surprise.He，like many adults，had become so used to the rubbish ar4．如图所示，半径为R的半圆柱体置于水平地面上，在其右端点A点的正上方P处有一可视为质点的小球．小球以某一初速度水平向左抛出，其运动轨迹恰好与半圆柱体相切于C点，∠COB=45°，重力加速度为g，则小球从P点运动到C点时的水平位移为（1+$\frac{\sqrt{2}}{2}$）R，时间为$\sqrt{\frac{（1+\frac{\sqrt{2}}{2}）R}{g}}$．