I can't be entirely sure but I think the reason "the tourist carries a backpack" is not allowed is because there is a difference between "niesc" and "nosic". one is something you are doing right now (i am carrying a backpack) and the other is habitual (i carry my purse whereever i go). (this is just my russian knowledge so someone please correct me if I'm wrong!!!!)
I also said carries but I see your point and I do understand there is a difference between niesc and nosic - good observation - thank you
I thought nieść meant 'carry' and nosić meant 'wear' as in a piece of clothing. I can understand why 'nosić' wouldn't be accepted for non-clothing items, but I don't understand why the habitual 'carries' isn't accepted here as a translation of 'niesie'.
Well, 'carry' is definitely a Verb of Motion, and those do show the difference between Present Simple and Present Continuous.
So "nosić" means either "to wear" or "to carry".
"nieść" means "to be carrying". "mieć na sobie" means "to be wearing".
noun [C] /ˈrʌksæk/ UK › a bag that you carry on your back plecak
Well, you learn something new every day. I would instinctively have said "backpack" or "rucksack" (UK, perhaps a bit old-fashioned). But going by Google Images, the expression "bag pack" does indeed exist, and would also appear to fit the bill.
"niesie" does not translate to "is wearing" (although "nosi" translates to both "carries" and "wears"). That would be "Turysta ma na sobie plecak".