When one tells me a sentence and then asks me "isn't it?" and I want to answer that I agree with him. Then what's the correct answer?
Yes, it is.
No, it is.
Because if I say "yes" to the question "Isn't it" it may be understood that I agree it is not. For example: A: "Isn't it?" B: yes. Meaning I don't agree, it says I think it's indeed not true. As an English learner I found it very confusing.