Помогите решить английский (final test)

doing it in this letter. We really love the city. It is so green and so clean. It is situated on the Potomac River, on a piece of land called the District o f Columbia, which is why people call the US capital Washington, D.C. It is not the biggest city in the United States, but it is the most important. The buildings are not very tall, the streets and avenues are straight, green and beautiful. The longest and the biggest avenues are named after American states. We have already done the centre of the city. We have been to the White House seen the Capital. The Capitol is really great. This is where the United States Congress meets and makes laws. The building of the White House is very beautiful with tall columns and the flag on the roof. It is the US president's residence. This is where the president lives and works. It is one of the most famous buildings in the world. Its name comes from the fact thet is it a white house. Tourists can't see the part where the president lives, but they can see the Red Room, the Blue Room and the Green Room and some other rooms. By the way, the city is famous for its museums. I have been to the Natural History Museum but I haven't seen the others yet.