Look! People are gathering to get water from a huge well in the village of Natwarghad in the western Indian state of Gujarat! ①Because of the large population on the earth, the world is ________hungry, it is ______be thirsty for water now. The world's population has reached 7 billion. And it could possible grow to 15 billion by the year 2100.

    ②On the other hand, about 97% of water on the earth is sea water which we can't drink or use for watering plants directly. Man can only drink or use the other 3% of fresh water which comes from rivers, lakes and underground. And we can't even use all of that, because some of them has been polluted.

    Now more water is needed. The problem is: can we avoid a serious water shortage later on? Firstly, we should all learn how to save water. Secondly, we should find out the ways to reuse it. Today, in most large cities water is used only once, but it can be used again .Even if every large city reuse its water, still there would not be enough. What could people turn to next?

    The sea seems to have the best answer. The sea is very big. Look at the map of the world, there is more sea than land. It covers three quarters of the earth. All that needs to be done is to get the salt out of the sea water. Scientists are trying to find a cheaper way of doing it. So you see,③如果我们可以找出解决方法，我们就不会有干涸（dry up）的危险。

材料一  越南战争历时12年，参战美军人数最多时达50多万，花费1650亿美元，是美国，二战后陷得最深、拖得最久、代价最大的一次以失败告终的侵略战争。1968年，反战示威游行遍及美国各地。1969年1月，在尼克松就任总统时，华盛顿上万名群众，高举着“尼克松是头号战犯”、“尼克松是亿万富翁的工具”等标语牌走上街头，举行大示威，吓得尼克松只好躲在防弹的“玻璃罩”里发表“就职演说”。

材料二  2012年5月，美国总统奥巴马28日在华盛顿市区的越南战争纪念墙前发表讲话，反思越南战争，表示要牢记越战教训。他说，越战是“美国历史上最沉痛的篇章之一”。雀讲话中，奥巴马强调，美国永远不应忘记越战的教训，战争的代价巨大，更会造成无辜平民的严重伤亡。他表示，战争本身并不光荣，应该受到厌弃。他说，越战的教训包括雀派出士兵参战时，应有明确目标和战略，领导人应对国民坦言战争的风险与进展，同时做好撤出部队的计划。