Arbitrary Duo strikes again. However, please copy and paste your full sentence. Sometimes there are other errors which the individual doesn't notice.
I think that at least 5 times I've reported "errors" to Duo and then wished I could delete the report, because as soon as I got back to my response, I saw a mistake in my answer which made Duo's rejection valid.
All of the above. The only problem is when Duo rejects one of them as invalid when there's nothing to suggest which one is right. That's arbitrary. I report such failures on Duo's part whenever they happen.
I think it's actually better to be aware of the multi-subject possibilities than to have them filled in, because not having the subject stated is a common feature of the spoken language. We just don't have the context that fills in the blanks, as in a normal conversation.
Does any one have any links to other sites to help with this section please, I am totally baffled? Duo has put in too much at once (again) and really it should be broken down into smaller bites. The explanation is an overview that has not got enough information to use for each sentence.