OMG, my first reaction, and then there were even seven comments under this exercise :D I guess there are eight of them now..but still awesome!
I'm not sure if that is really wrong, but I think native speakers would always include er here, it makes the sentence nicer/better.
It does accept that but as i understand it, the "er" is used since you don't know what's inside. If you'd want to say thst the blank is in the box you wouldn't use it
What are the connotations in Afrikaans? I'm curious, because the German version, "Dose" can have an entirely different meaning. But it's one I wouldn't want to write here, lol.
"What is (it) in the box?"
Using "it" is also OK because both sentences ask what/who the subject is.