完形填空
Natural resources are things that we use that come from the earth. Our natural resources are limited(有限的). This means that they will not1forever. Some are renewable, like when you plant a new tree when you cut one down. Others are not renewable, like when you dig coal(煤) out of the 2Once it is used, it is gone.
People realize the 3 that the earth's natural resources are limited, and can do things to help conserve(节约) those resources.4you try to conserve a natural resource, you try to use less of it, so it does not get used up so5One way that people conserve fuel, like gasoline, is by riding a bicycle or walking when the6is short instead of driving everywhere.
Water is a very important natural resource because we all need it to stay 7We can conserve water8making sure that our pipes and taps do not leak(泄露). We can also make wise choices to conserve water, like only using the dishwasher or washing machine when they are full. Everyone can make contributions to protecting natural resources.
Ti+2MgCl2 ，若要制得96 g 钛，计算至少需要镁的质量。
运会中，牙买加选手博尔特是一公认的世界
飞人，在“鸟巢”400m环形赛道上，博尔特在男子100m决赛和男子200m决赛中分别以9.69s和19.30s的成绩破两项世界纪录，获得两枚金牌。关于他在这两次决赛中的运动情况，下列说法正确的是