题目内容：

阅读短文及文后选项，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。

March 20th is World Water Day every year. According to a report from the United Nations, more than half of the world's major rivers have serious water loss and are polluted.

The Yellow River, the world's fifth longest river, watered some of the oldest farms  on earth.

1.Its source（源头）on Qinghai-Tibet Plateau is drying up. In most of the past 35 years, it didn't reach the sea.

The Nile in Egypt, running 6, 650 km, is the longest river in the world.2.Now it is down to 2 billion m³ or so. Australia's Murray River reaches the sea only every other year. One fifth of America's Rio Grande has no water, either.

3.

Mostly it’s damming（筑坝）and global warming that make rivers dry.4.Now about 45, 000 of them lie across the world’s rivers. They hold back around 15% of the world's fresh water from running to the sea.

5.Warmer weather takes water away. The glacier（冰川）are becoming smaller. The source of the Yellow River is drying up because of it. Global warming has had certain effects on water sources. Droughts （干旱） happening around the world make people pay more attention to this fact.

A. Dams provide fields with water and make power.

B. How does it happen?

C. It used to carry 32 billion m³ of water a year.

D. But now it has a serious problem.

E. Global warming is making things worse.