I wonder if someone could help with a grammar debate a couple of ESL teacher friends and I are having. This is a multiple choice question from an IELTS test.
He ________ gone to work yesterday. John was there all day and nobody saw him.
- mustn't have
- wasn't have
- can't have
Source: PDF file p2, Q34
The correct answer to the blank according to the test was "can't have" gone. One American ESL teacher disagrees, saying that answer is incorrect, and should read "couldn't have" gone (which wasn't a possible answer).
I have two questions.
Which of these two modal phrases (not sure if that's the correct grammar term) is proper;
I believe the second sentence is saying that "nobody saw John" and doesn't refer at all to the subject of the first sentence, where my friend believes the second sentence means "nobody saw the subject of the first sentence, and John didn't see the subject of the first sentence either", on the basis that the first sentence gives context to the second. Which is the correct reading?
Also, my friend teaching ESL thinks that "can't have gone" is technically correct, as any given phrase should have only one past tense element, excluding passive voice, which uses V3 (past participle) in every tense. He also thinks that "couldn't have gone" is a valid answer because of it being in common use, and was not included as an option in order to avoid confusion.