here I am again.
I do know about How + adverbs or adjectives (e.g.: How tall is he?, how handsome is he?, how deep is the river?..); however, I'd like to know three little things,
First: What is this rule's name? If there is one. (The grammar topic which talks about it);
Second: Is "How + adverbs or adjectives" always complements of the verb? E.g.: How deep is the river? - It is 100 feet deep - 100 feet deep is the complement of the verb Is, since it's a linking verb; therefore, How deep" means = "100 feet deep" which is the complement, so, is it the complement being placed in the beginning?
Thirdy: Could I say: Is it how deep? If not, why? What rule talks about placing the adverb in the beginning of the sentence?