I found this test question on the internet and apparently the author says the correct answer is ‘knew’ not ‘know’
The movie Jaws, directed by Steven Spielberg, hit the theaters in 1975 and was a huge hit. Millions saw the movie, and even those who did not
know / knew
the story.
According to someone who replied to the author’s question, the answer is ‘knew’ since ‘see the movie’ is omitted behind ‘even those who did not’.
‘Know’ seems just fine in that context and it’s way tricky to use ‘knew’ and I don’t think people would prefer writing or saying in such a confusing way. Is it possible to omit a phrase that has a verb in it?