Debbie,
You're on the right track. The stakeholders' communication requirements can be found in a number of places, starting with the project charter (at a high level), the stakeholder register, the stakeholder management plan, etc. For the exam, focus on who communicates with stakeholders, the PM's relationship with key stakeholders, and how stakeholders influence the project (active vs disinterested, etc). The exam won't attempt to trick you by providing you the same answer in different forms.
- Steven