The wood powder from wood shaving will get into the lungs of the rabbits and the human who breathe the surrounding area. Thus, wood shaving is bad news.
I click Other. I use hotel size towel. As they pee at the corner, the towel gets wet, I then switch the towel to the other side, when that side is also wet, I'll change towel.
I used to use litter tray. The problem is, as they pee, the urine moves around the tray, and some gets in their feet, their fur then get matted.
So towel to me is the best choice, it soaks the urine, and no rabbit can lick on the towel neither.