"The workers travel by trams and buses."
Translation:A munkások villamoson és buszon utaznak.
is there a reason why the English sentence is trams and buses (plural) while the Hungarian is villamos és busz (singular)?
No good reason. "By tram and by bus" would be fine. It's not really possible to tell from the Hungarian whether there's one tram involved or more than one; the same is true when you say "by tram" in English. It only indicates the means of transportation, not the number.
I think it might have to do with the "general statement" issue where English tends to use plural while Hungarian uses singular. So, both versions should be accepted.
no, because "by tram" would also be general. I think your point justifies the word "workers" in english and would explain if it was "a munkás" in Hungarian.