1 . 阅读下面材料，在空白处填入1个适当的单词或括号内单词的正确形式
The Rio Grande is one of the most important rivers in the US. But unlike other 1 （significance）rivers, it is not used for shipping. 2 makes the Rio Grande so important is its location. Since 1848, it 3 （be）the official border of Texas, the US and Mexico.
The river, 4 （measure）around 1,900 miles, is the 5 （five）longest in North America. Because the river twists（蜿蜒）so much, it 6 （occasion）changes its course. The river starts in Colorado and extends downward to the Gulf of Mexico.
The Rio Grande today is mostly used 7 a source of drinking water. Sadly, much of the water has been used up and parts of the river are almost dry! This is because people take 8 （much）water from the river than the river can get back from rain and other sources. Experts are working to correct this, though, with hopes of restoring the river to its past 9 （strong）.
Today, the Rio Grande is a popular tourist destination. Though borders like the Rio Grande separate the US and Mexico, they are also shared spaces. The Rio Grande is therefore 10 symbol of friendship and peace between two peoples.
