Вставить a/an, ... обозначают пропущенные a/an 1)... Mississippi is ... longest rivar in ... USA. It is such ... beautiful

1) Mississippi is the longest river in the USA. It is such a beautiful river.2) Niagara Falls is a famous place in the North America.3) The Colorado River cut a canyon in the desert rock. 4) Is the Death Valley fairly far from the Grand Canyon? 5) The capital of the US is Washington, D.C.6) I have never seen the Uluru Rock. It is such unusual place. 7) What do people usually do on Christmas Day?8)The Great Barrier Reef is a popular place with tourists.