U7
Grand Canyon-seen anything like;look down;above the place;longest;on the river;learn about;11,000;25-mile-trip;changes;7,000;levels;drops;photograph.
空格处答案.
U8
Las Vegas-ever visit; this terrific town;a great night out;driving down;offer;on both sides of;who want to;You can take;are famous for;Many visitors;Take time; past;a great time.