It can mean many things either you need to fill in by using context clues or your teacher might have pick a book with some inappropriate slang or vulgar in it and had to blank it out. Or it could mean blanks as in a type of firearm cartridge that contains gunpowder but no projectile
you either have to fill it in,context clues, or the person wanted it to be a mystery or could have done it by accident there can be many reasons behind it
