下列可以判定两个直角三角形全等的条件是（　　）

如图所示的闸刀开关说法不正确的事（  ）

唐朝时已出现白瓷，邢窑白瓷名满天下。《匍说》记载：古代烧制白瓷，必先用磁石在釉水中搅动，吸走铁屑，这样烧制出的白瓷才不会有黑斑，这种方法开创了现代磁法选矿的先河。这表明（    ）

阅读短文，判断正误。
    Hello, friends! Let's go on a trip to Beijing. Beijing is the capital city of our country. It's in the north of China. There is a big square in this city. Do you know its name? Its name is Tian'anmen Square. In Beijing, you can see the Bird's Nest(鸟巢). The 2008 Olympic Games were held in it. And you can see some old buildings, such as the Palace Museum. The Great Wall is also very famous in China. It's very old and long.

近年来，全球气候变暖问题日益严重，北极冰川融化速度也随之加快。北极冰川消融，将使北极熊等北极特有物种面临灭绝的威胁，还有可能造成海平面升高，对沿海国家和地区造成重大影响。这说明（    ）

①我们要珍爱生命，就要珍爱我们所生活的大自然                       ②人类对气候变化和自然灾害无能为力

③破坏人类赖以生存的生态环境，最终受害的还是人类自己       ④地球是人类共同的家园，关爱地球就是关爱人类自己