下列句子中划线词语使用不恰当的一项是（    ）

   A plant makes its own food in its leaves . Water comes to the leaves through the roots . Air gets into the leaves through very small holes . The green coloring in the leaves uses the water and air to make the food for the plant . It also needs sunshine because a plant can make food only when the sun is shining.
   Animals and people could not live without green plants . They both eat plants . People and some animals also eat the meat of some animals and these animals eat plant

现有8g Fe₂O₃和CuO的混合物，进行如下实验：把混合物全部加入到50克足量的硫酸溶液中，完全溶解后，滴加溶质质量分数为8%的氢氧化钠溶液，滴加氢氧化钠溶液的质量与生成沉淀质量的关系如图所示．回答下列问题：

①求所用硫酸溶液溶质的质量分数．

②求a的取值范围．

③若a=30，则将此16克混合物用过量的一氧化碳充分还原，求冷却后所得固体的质量．

人体呼吸系统的组成是（　　）