橡胶树通过割皮可获得橡胶制品的原料--白色乳汁状的液体．若右图表示橡胶树茎的切面，请问乳白色的液体是从图中的什么部位流出来的（）A．a与cB．b与cC．aD．c-生物

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• 在绿色开花植物体内，运输水分和无机盐的是导管…______．-生物
• Huge amounts of oil have been found on the Gulf of Mexico floor, the effects of _____ are still bein
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• 下列关于导管和筛管的叙述中，错误的是（）A．同位于根、茎、叶中B．同属于输导组织C．都有输导作用D．都是死细胞-生物
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