The most important thing to consider in answering this question is to ensure you are presenting a clear well structured argument. That means you need a point of view of what CAUSED the great rebellion that is consistent throughout. An easy structure would be to argue that it was a combination of his treatment of his sons and his baronial policy. This is because the barons support was necessary for his sons to launch the great rebellion. This argument is simple as it uses the wording of the question but can be well justified throughout the essay. It is easiest to write 3 main paragraphs. The first should analyse how Henry's treatment of his sons contributed to the great rebellion. Within this paragraph it should be made clear why this is not the only factor. This is because Henry's three sons alone could not launch a rebellion. They needed baronial support. Evidence used to indicate this is beneficial.The second paragraph should focus on the baronial policy (e.g. the cartae baronum) and how increased control over the barons' led to revolt. It should include evidence. The reason why the baronial policy contributed should be explained. Finally a third paragraph on the role of Louis VII of France should be written. It should explain it is secondary factor that contributed but did not cause. A well developed conclusion tying the essay together is crucial at the end.