action in progress / completed action

[Verona_82]

Dear teachers,

Do all the sentences below sound fine to you? The original one is:

The phone ______ (ring) as I ______ (leave) the house.

That's what I came up with:

The phone was ringing as I left the house (the former considered a process, the latter considered a completed action)

The phone rang as I was leaving the house (the former viewed as a completed action, the latter - as a process)

The phone was ringing as I was leaving the house (two processes happening simultaneously)

[billmcd]

Dear teachers,

Do all the sentences below sound fine to you? The original one is:

The phone ______ (ring) as I ______ (leave) the house.

That's what I came up with:

The phone was ringing as I left the house (the former considered a process, the latter considered a completed action)

The phone rang as I was leaving the house (the former viewed as a completed action, the latter - as a process)

The phone was ringing as I was leaving the house (two processes happening simultaneously)

Yes. They are all OK.

[Verona_82]

Thank you!
But the problem is as follows. What if we extend the original sentence, adding "but I didn't answer it'?

The phone ____ (ring) as I ____ (leave) the house, but I didn't answer it.

The key gives "the phone rang as I was leaving the house, but I didn't answer it" as the correct alternative, implying that the process of leaving was interrupted by the call.
I do totally agree with the key, but I cannot explain why the other two alternatives are incorrect. Does it have anything to do with 'but I didn't answer it'?

[5jj]

The addition of 'but I didn't answer it' changes nothing in this sentence. All three versions are still possible.