I understand that you are trying to reinforce nuance in this lesson, but there are very, no, quite, no, a lot of different ways to say the same thing in English. This is one of the most annoying lessons by far.

Are 상당히 and 꽤 interchangeable? I noticed a lot of these words can basically mean the same thing, but is there a time when one is better than the other?

OMG. I cannot pronoun the sentence above.

Dont really and quite mean the same thing in this context?? Why is one accepted and the other not?

'That is extremely expensive' is wrong?