We ask Зачем? when we want to know the cause of what is happening. And we ask Почему? to know the purpose of it.
(My native language is russian, so I'm sorry if I make mistakes in English :) )
"Зачем?" is more like "what for?", but can also be translated to "why?"
"Почему?" is "why?"
Hold up. I think the explanations of KrICEtON and JanisaChatte are somewhat contradictory. According to KrICEtON " Почему" is used to inquire the purpose of something i.e. "what for" while for JanisaChatte it's "Зачем". Which one is it then?
"What does he read so much for?" is very informal and stilted. IMO, a more natural translation would be "Why does he read so much?"
Your translation is more natural English by far. So many of these discussions over translations into English are arguments about how literal or colloquial a translation should be, and they are tiresome. The problem arises, I think, because so many of the course developers are not native English speakers. The purpose of the course is not to teach English, after all.
"What is he reading so much for?" was marked wrong, in favor of "What does he read so much for?".
Is present continuous not acceptable here?
I don't understand why my answer "For what does he read so much?" is wrong.
I don't think that's grammatically correct in English. The correct should be "What does he read so much for?"
I admit that it may sound stilted, but I assure you that it is grammatical. We don't have to end English sentences with prepositions. "What" is the object of the preposition "for."
There is no difference in meaning between "What does he read so much for?" and "For what does he read so much?" It may help you to see my point if you recognize that the word "reason" or "purpose" is implied in both English sentences.
Of course there's no difference in meaning between them, but the second one doesn't really sound right (it might be technically correct, but it just sounds weird to me)
Which is the function of "так" in this sentence? Is it an expression, saying "так много" instead of just "много"?