The cover is in Polish but this book include "only" 1000 Trios in English so it's accessible to anyone who wants to get grip on what new task is. Trios are tree separeted sentences that miss exacly one word. The word needed is same for all of them and in exacly the same form. For example:
1. There has been a steady ... in the number of guidebooks published recently.
2. As she'd taken on a lot of extra responsibility at work, Martina felt justified in puting for a ...
3. The ancient farmhouse had been build on a slight ... overlooking the vast open plain.
Answer for this Trio is "rise"
I've found this especialy valuable because of lack in similar publication covering this new type of task. Trios are put in order from easer to harder so begining of this book is CAE level and end is CPE level.