1.
3 The biggest river in the USA - Mississippi.
4 The capital of the USA - Washington
10 The US state in the west country famous for its beaches - California
11 The lowest, driest and hottest place in North America - Death Valley
12 The lake situated in Death Valley - Racetrack Playa
2.
2......isn't there?
3 does it?
4 ......isn't she?
5 ........haven't they?
6 ...........doesn't it?
7..............weren'the they?
8...............do they?
9................won't you?
10..................haven't we?