Natural resources are things that we use that come from Earth.  Out natural resources are limited(有限的). This means that they will not1 forever.

    Some are renewable, like when you plant a new tree when you2one down. Others are not renewable, like when you dig coal out of the 3.Once it is used, it is gone. People realize the4that Earth's natural resources are limited, and can do things to help save those resources.5you try to save a natural resource, you try to use less of it, so it does not run out so 6 One way that people save fuel, like gasoline, is by riding a bicycle or walking when the 7is short instead of driving everywhere. Water is a very important natural resource because we all need it to stay8. We can keep water9making sure that our pipes and taps do not leak(漏). We can also make 10 choices to save water, like only using the dishwasher or washing machine when they are full.

    Everyone can make contributions to protecting natural resources.

用显微镜观察草履虫时，经常在临时装片的培养液中放一些棉丝，其作用是（    ）

“春种一粒粟，秋收万颗籽”，一棵参天大树也是由一颗种子发育来的，其实是因为种子中包含有发育成一株完整植物的（  ）

阅读下列材料：

材料一：1942年1月1日，美、英、苏、中等26个国家的代表在华盛顿签署了《联合国家宣言》。《宣言》指出：各签字国政府保证使用其全部的经济和军事资源对法西斯三国同盟成员国及仆从国家作战，保证不同敌国单独缔结停战协定或和约。

材料二：1945年2月，美、苏、英三国首脑召开了雅尔塔会议，就德国处置问题、波兰问题、对日作战问题和联合国成立问题等达成了协议。会议结束后，罗斯福认为战后美苏关系将是一种竞争的关系，只是不要在条件尚不成熟时演变成战争。会议结束时，美国代表团的一些成员是带着“别了，下次战争再见”的心情离开的。