Different forms of question

There are so many ways of asking the same question,

what is the longest river in China
what is the longest river that is in China
what is the river in China that is the longest
what is the river that is the longest in China

is there any other forms ? Which one is more formal and commonly used ?

Thanks
William

Thank you and I like to hear that too, it will certainly become less complex for my Natural Language Processing application

Ok, thanks about that, but in this context I am more concern about the forms of the sentences, that's why I forget about it. Thank you.