My tips:
1) You should always be problem solving as a PM. so , pick the best response from PMBOK''s perspective that has resolved the issue/problem statement in the question.
2) Sponsor and the customer should be the absolute last resort to contact. As a PM, one should always try to resolve first, and if nothing else works- then contact the sponsor or customer. Except in the case of business case where PM can provide recommendations to sponsor to add/edit the business case contents.
3) During your preparation, ask yourself why is this an ITTO of this process.
This should help. All the best !