依次填入下面横线上的词语，最恰当的一项是（    ）
生活如海，            ，泛舟于海，方知海之宽阔；生活如山，            ，循径登山，方知山之高大；生活如歌，          ，和曲而歌，方知歌之动听。同学们，让我们多一些宽容，也就多了一份理解，多了一份信任，多了一份友爱。愿你我的胸怀像大海，无所不容；心宽如天空，无所不包！

某物理实验小组的同学安装“验证动量守恒定律”的实验装置如图1所示．让质量为m₁的小球从斜面上某处自由滚下与静止在支柱上质量为m₂的小球发生对心碰撞，则：

求证：

（Ⅰ）直线EF∥平面ACD；

（Ⅱ）平面EFC⊥平面BCD．

                                B     

    Hippos(河马) live in Africa(非洲). They are one of the world's largest land animals. Here are some interesting facts about them.

●Where are hippos born?

    Hippos often give birth in the water. The hippo babies get out of water right after birth to take their first breath.

●How quickly do hippos grow up?

    Hippo babies nurse both under water and on land for a year. Then they stop taking their mothers' milk but they are still with their mothers until they are eight years old. Then they move out.

●What do hippos love?

    Hippos love water and they spend most of the day in it to stay cool. The Hippo can breathe, see and hear when its body is under water because its nose, eyes and ears are on the top of its head.

●Do hippos swim better than people?

    Yes, they are great swimmers and they can hold(屏住) their breath for five minutes. Hippos can even walk under water along the bottom(水底) of rivers and lakes.

如图所示，在圆圈内分别填入正确的电表符号，使开关闭合后两灯都能发光。