"We are not looking at the last pear."
Translation:Nedíváme se na poslední hrušku.
I just got this wrong by (stupidly) changing my answer at the last second to include "tu."
My answer to your question is a GUESS is based on logic, rather than on grammar: If it's the last pear, it's the only pear there. If there's only one pear there, it's not necessary to indicate which pear you're talking about, since it can only be the one that's sitting there.
This logic fails, however, if the pear is the last one in the refrigerator and you don't know that there's only one there, but are asking a general question... Oops. Maybe someone else can give a better explanation!
For me, word order is one of the most challenging aspects of learning Czech. I read the rules, but repeating exercises over and over and over really helps it "stick." Over time, I've started recognizing what sounds (more) right. but I'm definitely not even close to 100%! Maybe that's my version of "listening to the music of the language."