How do you know which universities are realistic choices?
Ideally you’ll do so darn well in your exams and be such a good-at-everything freak that nowhere would refuse you. But that’s not possible for all of us.
Fortunately, most students aren’t at the other end of the spectrum either, where their choice is limited to universities who charge $10 a degree (post and packing extra).
Most students have their choice of most courses, within reasonable limits. With three Ds, you won’t be doing medicine, but the crop is still plenty pickable.