The thing is, what ever they dont ask in 2/4 unit they will ask in three unit.
Theyve basically covered probability, and binomial was pretty tricky in 4 unit. So it wont be focused on as much.
One thing they will hammer is motion. In two unit it was only that easy graph, and in 4 unit it was that bread and butter circle motion that everyone should be able to do. Motion will be a big part of three unit for sure.
Also watch out for induction. That induction in 4u was pretty straight forward, and its a pretty standard one that ive seen before. So they will give a painful induction in three unit.
The general rule is that if 2u/4u are simpler, 3u is going to be a killer. Even though people thought 4u was hard, BOS would see it as not as hard as other years. And the 2u is just a dead giveaway.
Good luck to everyone.