正方体有4个面．

严复是戊戌变法时期的启蒙思想家，他译著的哪本书在当时影响最大？（  ）

如图，弹簧测力计挂着重为10N的合金块，让其浸没水中，使容器内水面由16cm上升到20cm，容器内底面积为50cm²，（取g=10N/kg）。求此时：

（1）容器底受到的水的压强；

（2）合金块的密度；

（3）弹簧测力计的示数。

如图所示为一直角棱镜的横截面，$\angle bac={90}^0,\angle abc={60}^0$，一平行细光束从O点沿垂直于bc面的方向射人棱镜，已知若不考虑原入射光在bc面上的反射光，则下列说法中正确的是                    （   ）

    If someone is lost in a forest( 森林 ), he needs only study the trees around him carefully to find his way. On this half of the earth, he will find that the side of the tree with the most leaves and branches(树枝 ) is the south side. Also, by checking the tops of the trees, he will find that they lean(倾斜 ) to the south too.
    Another sign( 标志物) for him to know where he is going is found in the bark.( 树皮) That is brighter on the south side.The remanining(树桩 ) of a cut tree is also a finder, for its rings can give him another sign. The rings will be thinner on the south side and thicker on the north side.
One more sign: some very small plants grow at the foot of a tree and they point to the north.