Final answer:
The phrase 'From overseer to adviser' best describes the shift in missionaries' roles due to the rise of nationalism, indicating a move from authority to guidance.
Step-by-step explanation:
The phrase that best describes the shift in the role of the missionary in response to nationalism is a) From overseer to adviser. This shift reflects the changing dynamics between colonizing powers and local populations as nations began to assert their independence and develop their own national identities. In this context, missionaries had to adjust from a more authoritative position to one where they served as guides and supporters of the local people's spiritual and sometimes even social development.