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    A man lived in a village. He had an old cat at home. The cat couldn't run fast and bite，because she was so old. One day, when she saw a mouse, she jumped and caught it. But she could not bite it. The mouse got out of her mouth and ran away.

    Then the man became very angry and began to beat the cat. The cat said, “Don't beat your old servant. I know I'm old and can't kill a mouse. But I have worked for you for many years, and I still want to work for you. Be kind to the old, and remember what good work they did when they were young."

    When the man heard that, he realized that he was wrong.

在制作洋葱表皮细胞临时装片时，把载玻片放在实验台上，用____在载玻片中央滴一滴____；而制作人体口腔上皮细胞装片时，则在载玻片中央滴一滴____，其浓度为____，目的是维持口腔上皮细胞的____，有利于观察．盖盖玻片时应用镊子夹起盖玻片，使它的____先接触载玻片上的液滴，然后____，以免____．

《圣经》里把两河流域描绘成“人类幸福的伊甸园”。在这里曾经孕育的文明国度是（   ）