某兴趣小组对部分变质的氢氧化钠固体进行提纯，设计了如图操作流程：请回答：

中国对钓鱼岛拥有无可争辩的主权。近代日本曾通过哪个不平等条约割占了包括钓鱼岛在内的台湾全岛及附属各岛屿（    ）

随着历史的发展和社会的进步，互联网进入人们的生活，网络交往成为人们生活中不可或缺的一部分。人们离不开网络交往的原因在于（    ）

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    A bag is useful and the word "bag" is useful, too. Here is an interesting phrase, "to let the cat out of the bag". In meaning it is the same as "to tell the secret". And there is an old interesting story about it. Long ago, when farmers wanted to sell chickens at the market, they would usually throw the chickens in cloth bags. But cats were cheaper than chickens at that time, so many farmers would put cats into the cloth bags but not chickens.

    One day, a woman asked a man for a chicken. The man gave her a cloth bag in which there was a cat. The woman begged to see the chicken. When the man opened the cloth bag, a big black cat ran out. Not a chicken! The man's secret was out and everyone knew it.

    Now when we say someone gives away a secret, we say "he lets the cat out of the bag". And that is the story where the interesting phrase came from.