What is the reason for this?
What is the reason of this?
What is the reason why you tell me that?
Which one is correct?
What is the reason of this?
What is the reason why you tell me that?
Which one is correct?
are you sure? because velisarius told me that the second and third one was wrong.They are all possible.
According to you, it can be "terrible"!, but for English grammar, if it is correct, I will not mind what one is thinking about it.To be clear, I don't mind "the reason why", where you might claim that "why" is superfluous.
"What is the reason why you tell me that?" That's a terrible sentence. A native speaker would ask "Why do you tell me that?", or more likely "Why are you telling me this?"
If you insist on the sentence, you could use "the reason that..." or omit it entirely: What is the reason you're telling me this?According to you, it can be "terrible"!, but for English grammar, if it is correct, I will not mind what one is thinking about it.