谚语诗词中蕴含科学道理.下列说法正确的是( )
A:“真金不怕火炼”说明黄金的熔点很高
B:“众人拾材火焰高”是指可燃物越多,着火点越低,越容易着火
C:“百炼成钢”与“只要功夫深铁杵磨成针”蕴含的化学原理相同
D:“满架蔷薇一院香”的原因说明分子在时刻不停地做无规则运动
已知如图为一几何体的三视图.
(1)写出这个几何体的名称____
(2)若主视图中长方形较长一边的长为5cm,俯视图中三角形的边长为2cm,则这个几何体的侧面积是____ cm2.
解关于x,y的方程组ax+by=93x-cy=-2时,甲正确的解出x=2y=4,乙因抄错了c,误解为x=4y=3,求a,b,c的值.
Steve's activity on Sunday
In the past
He spent most of the time 1.
He learnt it from his 2 and he is good at it.
Now
He spends at least 3 hours collecting rubbish.
He would like to protect the beach.