Lol, come on, that's obviously not the question. Of course they mostly had one child per pregnancy, with the occasional twins / triplets. Why would anyone think otherwise, or even ask.

The question is how many children the average homo erectus would have, not how many children per pregnancy. I would say it must have been higher than current numbers (so, higher than 2 per couple), probably quite a bit higher, to account for extreme child mortality - otherwise populations would dwindle fast.

I'd be very surprised if it was less than 4 per couple or something.