Why 볼 instead of 읽?
Koreans use the word 보다, which literally means "to see", also when they talk about reading. In fact, I'm sure using 보다 is actually more common that using 읽다.
A book to read tomorrow.
this sentence is wrong?
Nope, that's correct. You can also say "a book (that) I/you/she/he/it/we/they will read tomorrow"
Or "A book that will be read tomorrow"
볼 is so different from 읽
This should not have a period at the end because this is not a sentence.
Thank you. I have just replaced this exercise with a new one without a period.
I put, "내일 읽을 책," and it was correct. :)
why I can't listen to "읽을" sound
The word 읽을 isn't in the sentence.
내일 볼 책
볼 is used which is the future form of 보다 which means "to see". 책을 보다 means to look at a book, but it also means to read a book depending on the context.