Sagar,
I agree with Ahmed, that the CCB should be the correct answer. The CCB controls your project's baselines (such as scope, budget, and schedule).
However, I think I can understand why whoever wrote that question said the answer is 3. For massive, fundamental changes to a project, additional leadership buy-in is typically required. If management kicks off a project to accomplish X, and then later your CCB decides to only accomplish X/10 (without consulting senior management), you're going to have problems!