Translation:The passengers sit in a bus.
Is pasażer the same declination as syn --> snyowie?
Yes. Well, it's "synowie", but that's clearly just a typo.
'are seated' should be accepted
is it not correct to say "autobus" in english?
I believe it's a dated usage.
I also thought so ...
I would suggest using "on the bus"
In my case I had to select from only a few options, which only had "a bus", which made it sound pretty weird in English compared to the Polish translation.