I put 'car keys' instead of 'car key', I had a feeling I would be marked wrong for it, but that is how most people would say it. I've never said that, 'I lost my car key'.. But I've often lamented losing my car keys. I actually think it's probably right on duo's part to mark me incorrect, but still, I think I'm kinda right too maybe?
It's one of those things in idiomatic English. Maybe it comes from the days when you had one key for the ignition and one for the glove box and one for the trunk. A lot of people say "car keys" when it's really only one key you're after. Both are accepted now so just pay attention to the French.
I don't understand why "She lost her car's key" is wrong ????? Why is it not ok to use " 's " ??
The car is not owning anything. The owner of the key is the woman. Does this help?