Is Washington a capital of the USA?
Washington is a capital of the USA, isn't it?
Which city is a capital of the USA?
Is Washington or New York a capital of the US?
What is a capital of the US?(насчет этого не уверен, так как не могу придумать ничего кроме этого/ not sure about this 'cause I can't think of anything else)
Washington is not a capital of the US.