In Cambridge where I supervised, questions were generally set by the supervisors, not the lecturers. The usual group size in Nat Sci was two, though I supervised groups of medical students up to four, as I recall. Four male boaties could be fairly bumptious. Five feels more like a mini-lecture.

I did have an unfortunate tendency to talk and test their comprehension via essays, rather than attempt to assay it by questions. I don't think I was cut out to be a teacher.