"Worf has a book."
Translation:paq ghaj wo'rIv.
paqDaj ghaj wo'rIv is a legitimate sentence in Klingon, translating to, "Worf has his book." As in English, "his" might refer to Worf or to some other person. In fact, since Klingon -Daj does not specify gender or even life, it could also be "her" or "its".
wo'rIv paq is a legitimate noun phrase, meaning "Worf's book". This is not a complete sentence and does not mean the same as "Worf has a book.". In fact it is quite possible that someone else has Worf's book at the moment and that Worf has someone else's book in this exercise.