题目

Amazing Facts About ELF Owls The elf owl is mostly found in the southwestern parts of the United States and Mexico. During the spring and summer seasons, it moves to Arizona and New Mexico. It returns to Mexico for the winter. The elf owl doesn’t build its own nest. It lives in tree holes The elf owl is a yellow bird with dark wings. Its eyes are bright yellow and its feet are large. It is the smallest owl of the species, only about 12.5—14.5 centimeters long. It is also the world’s lightest owl, weighing not more than forty grams. In general, female elf owls weigh more than male o对物质进行分类是我们研究物质的便捷途径。现有以下物质：①塑料保鲜膜；②纯碱；③ 硝酸钾；④铝制易拉罐；⑤高铁的铁轨；⑥我国自主生产的圆珠笔头的圆珠；⑦PET制的犷泉水瓶；⑧磷酸二铵；⑨烧碱。对上述物质分类不正确的是A．属于复合肥的有③⑧ B．属于有机合成材料的有①⑦C．属于金属材料的有④⑤⑥ D．属于碱的有②⑨