题目

请认真阅读下面短文，从短文后各题所给的A、B、C、D四个选项中，选出最佳选项。 Just as we take care of our friends and families, our homes and Mother Earth take care of us. Our homes give us a place of shelter (庇护物) that 1 between us and the rest of the world. The earth is a(n) 2 giver of life and the keeper of our physical and spiritual needs. Her rich 3 bring us up, give us air, and offer us cooling shade. Her waters 4 our thirst. Yet it is easy to take both of these wonderful 5 of our gifts for granted. 6 the thanks you feel toward your home and Mother E下列关于空气的说法中，错误的是 A．空气中含量最多的元素是氮元素 B．空气是一种十分重要的天然资源 C．工业上从液态空气中分离出氧气的过程属于物理变化 D．若大量有害物质进入空气中，仅靠大自然的自净能力，大气还能保持洁净