I'm a little confused about the following sentences. Could you please tell me which one(s) is/are correct?
The first and the second chapter are difficult.
The first and the second chapters are difficult.
The first and second chapters are difficult.
The first and second chapter are difficult.
I believe #1 & #3 are correct, while #2 & #4 are incorrect.
But when seeing the answers to the Quora question "Which one is grammatically correct "The first and the second chapter is very difficult" or "The first and second chapters are very difficult"?", I wonder why they say #2 is correct.