Chores weren't popular at my house. My children didn't like to do chores. They always saw me do chores, but they hardly ever helped me dothem.

    A year ago, I made a game called "The Endless ChoreGame". It's really great. Here's how the game works.

    I make a card with forty squares(方框), and I write adifferent chore on each square. These chores can be easy and interesting likemaking dessert. Then my family roll the dice(骰子)to decidewhat chores we have to do. The card also has a few squares with fun things, like watching TV and singing. If you're lucky, you can watchTV when the others are doing the chores.

    My son likes the game very much. He goes to the kitchen happily every morning to do the game. It's really a good way to make my children do chores. You can have a try if you have the same problemas me.

铝热反应常用于冶炼或焊接金属，反应原理：．现高温加热铝粉和氧化铜混合物，使其充分反应．为检验反应后氧化铜是否有剩余，取少量反应后的固体，加入足量稀硫酸，反应后将锌片插入上层溶液中．

（已知CuO+H₂SO₄═CuSO₄+H₂O）下列现象能说明氧化铜有剩余的是（　　）

①改革试点——承认矛盾的特殊性是普遍性的前提

②总结经验——在试点中概括出普遍性原理

③扩大试点——将试点中获得的个性理论推广于改革

④全国推进——将矛盾的普遍性与特殊性有效衔接

如图5，△ABC中，DE是AC的垂直平分线，AE=5cm，△ABD的周长为14cm，则△ABC的周长为____cm。