联系课文内容，再联系生活实际谈谈你对下列几种能力的理解。

1．独立思考能力：                                                                                                                         

2．独立判断能力：                                                                                                                         

3．怀疑能力：                                                                                                                                 

建筑工地上有一个圆锥形沙堆，沙堆底面半径为2米，高1.5米．如果每立方米黄沙重1.7吨，这堆黄沙重多少吨？