backbacks造句

Students at the campus said there was some concern on campus but that they were more at ease after the police started searching bags, parcels and backbacks of people entering the libraries.
All solemnly agree the worst part of the trip was the first day in Costa Rica when the family stopped to look at crocodiles off a bridge shortly after 5 p . m . When they got back to their car, a window was broken and three backbacks were taken.
It's difficult to find backbacks in a sentence. 用backbacks造句挺难的