Humans use water for three basic purposes: agriculture, industry, and domestic and municipal use(water for drinking, cooking, cleaning, and so forth). And the amount of water (47) to each person decreases as the population grows, (48) the possibility of water shortages. Water shortages will not come all at once in every part of the world, just as the world’s population is (49) distributed by region, so is the annual (50) of renewable water. Rainfall and snowfall are (51) by uneven weather pattern sand landscape, and as a result, some areas of the world get more precipitation than others. This leads the uneven (52) of water all over the world.
Natural water scarcity has prompted many nations to try to increase their water supplies by building dams to catch water that otherwise would escape to the sea, or by sinking more and deeper wells. But these efforts can have (53) side effects that can contribute to water scarcity. Instead of building dams, some countries choose to increase their (54) to groundwater. But this practice increases the risk of over pumping aquifers (蓄水层).
Pollution also affects the water supply, reducing the available water by it toxic or otherwise (55) for human use.
Water shortages could also lead to international conflicts as countries (56) for limited water resources. Political tensions over water often appear when different nations lay claim to the same river, lake, or aquifer. According to the UN, more than 300 river basins and aquifers worldwide cross national boundaries are creating the potential for conflicts.

• A) accessI) unevenly
• B) positivelyJ) unfit
• C) deliberately K) starved
• D) compete L) raising
• E) negative M) approach
• F) distribution N) arising
• G) available O) supply
• H) determined