观察洋葱表皮细胞结构的实验步骤是[]A．制作标本、染色、画图、观察B．制作标本、观察、染色、画图C．染色、制作标本、观察、画图D．制作标本、染色、观察、画图-七年级生物

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• 阅读理解。 The idea of daylight saving time started with an American named Benjamin Franklin (1706-1790).
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• 生活在海水中的海带，其细胞中积累碘的浓度比海水中的浓度要高许多倍，而海带细胞仍能从海水中吸收碘，这一事实说明[]A．海带细胞的细胞壁有吸附碘的功能B．海带细胞的细胞质中-七年级生物
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