Những gì là những gì?
Should this be, "Who is whom?"
If you're going to use ‘whom’, then surely you'll also use the predicate nominative, so it's ‘Who is who?’ after all.
You're absolutely right! Thanks for the correction. I learned something today.
For the curious: https://english.stackexchange.com/questions/192794/whos-who-or-whos-whom
thế nào là thế nào ?
cái gì là cái gì?