It just occurred to me - is "bil" short for "automobile"?
Yes, or rather for the Norwegian version: "automobil".
can we use in this situation "jeg trenger en leiebil" ?
Yes, you can say that.
Why are both "Jeg må leie bil." and "Jeg må leie en bil." correct, when there is definitely an "a" in the English sentence?
The missing indefinite article: https://www.duolingo.com/comment/8777724
I see... Thanks!
Why was leiebil not accepted here, but was in previous section?? In previous section, to rent a rental car dounded redundant, but was accepted?????
Technically the English in the question doesn't say "rental car," just "car." You can report it if you think your answer should be accepted.
So can må and trenger be used almost always interchangeably? I realize the literal translation is probably different, but are there scenarios where you have to use one over the other?