I came across one of the questions founded in the TOEFL.
... is entirely up to him
(The correct answer)
-How he travels
(what I choose)
-How is he traveling
(what I thought to be correct, but didn't appear as an option )
-How does he travel
How could the third clause above didn't appear in the question? And it's a common sense for me to just say the first sentence above is correct but since I just followed the writing rules and couldn't even explain why I feel it's correct so I chose the second sentence.
I know that I can omit modal (do/does) in Wh- question, like 'who wants to be...', but 'how he travels...' is completely unrelated since there is 'he' there.
Is there any specific information on this topic in English grammar? What do we call it? Is it just fixed pattern? Perhaps it might be considered to be easy, but I miss this kind of things like a lot times.