Hi Rachel,
stakeholder analysis is, according to the PMBOK, A technique of systematically gathering and analyzing quantitative and qualitative information to determine whose interests should be taken into account throughout the project.
the output of stakeholder analysis is part of the stakeholder management plan which in turn is part of the project management plan.
I would select option C as the best answer. (option A was correct as per the 4th edition however in the fifth edition stakeholder management plan is separated from the communication management plan)