根据图中所给的边长长度及角度，判断下列选项中的四边形是平行四边形的为（　　）

有学者说：“对于中国人来说，这场战争是一块界碑．它铭刻着中世纪古老的社会在炮口逼迫下赶往近代的最初一步。”“这场战争”指的是（   ）

    Have you ever been sad because of failure? Please remember, for quite often achieving what you set out to do is not the most important thing.

    A boy decided to dig a deep hole behind his house. As he was working, a couple of older boys stopped by to watch. “What are you doing?” asked one of the visitors. “I want to dig a hole all the way through the earth!” the boy answered excitedly. The older boys began to laugh, telling him that digging a hole all the way through the earth was impossible. After a while, the boy picked up a jar. He showed it to the visitors. It was full of all kinds of stones and insects. Then he said calmly and confidently, “Maybe I can't finish digging all the way through the earth, but look at what I've found during this period!”

    The boy's goal was far too difficult, but it did cause him to go on. And that is what a goal is for－to cause us to move in the direction we have chosen, in other words, to cause us to keep working!

    Not every goal will be fully achieved. Not every job will end up with a success. Not every dream will come true. But when you fall short of your aim, maybe you can say, “Yes, but look at what I've found along the way! There are so many wonderful things having come into my life because I tried to do something!” It is in the digging that life is lived. It is the unexpected joy on the journey that really makes sense.

某小组同学对双氧水进行如下探究：

（1）图l中仪器①的名称：____，该装置中发生的化学方程式为____ 。 图l装置中的圆底烧瓶也可以用____ 替代（填仪器名称），该装置也可制取____ 气体(只填一种即可)。
（2）若将MnO₂与水泥按一定比例加水混合、凝固，制作成小块状固体。加入图2装置中制氧气。其中块状固体应放置在____ 处（填“A”或“B”），你的理由是____ 。
（3）利用图2装置反应一段时间后．需停止反应，其操作是____ 。