I have heard this sentence, said by somebody:
- Okay, let's check your homework. Sentence 1... correct, sentence 2... also correct, sentence 3 correct as well, and sentence 4... correct, too.
Now, I've really wondered why there's no is used. I suspect there's a pattern saying when we can omit the auxiliaries in such cases, so is there? I have searched about omission of auxiliaries in some ďictionaries, but, unfortunately, I was unable to find anything about such a sophisticated question as this one, posted by me personally.