画出格点△ABC(顶点均在格点上)关于直线DE对称的△A1B1C1;在DE上画出点P,使PB+PC最小;在DE上画出点Q,使QA=QC.
根吸收水分和无机盐的主要部位是( )
合理的历史联系是历史学习的常用方法之一,图空白a、d相对应处,应补填上
People have the belief ________ factories should produce fewer things from raw materials, ________ the supply is growing smaller and smaller.