小题1:D
小题2:C
小题3:D
小题4:C
小题5:A
小题1:根据文章内容The greatest of all for navigation（航海）, however, is the Amazon in Brazil（巴西）可知答案为D
小题2:根据文章内容可知答案为C
小题3:根据文章内容Then people can use the water not only to irrigate(灌溉) their fields but also to make electricity for their homes and industries.可知答案为D
小题4:根据文章内容the water in the rivers becomes polluted with chemicals and other materials.卡答案为C
小题5:根据文章内容大意可知答案为A