To help students understand the activity, play a class boardgame. Look for volunteers (or start with the JTE) to roll the die and answer a question.
For example, a volunteer student lands on the 5th box, "Which sport do you want to try?" and answers "I want to try rock climbing." Tell the class that the answer is right, but by this time, they will try to answer using who, that and which. If they have finished learning the unit, it would be pretty easy for them to answer, like "Rock climbing is the sport which I want to try.
Tell students that the questions is the hint of what they're going to use in the sentence: What - that, Which - which, Who-who.
I attached the document file so you can edit it freely.