Answer: Choosing a particular subject like "healthcare' to focus on
Step-by-step explanation:
There are various ways to narrow the scope of a research topic such as choosing a particular population, time period, location in the world and causes and the like. This will enable the research to be easier to do and cheaper as well.
Choosing a particular subject will not necessarily narrow a topic because the topic is most likely under a subject as well. Basing it again on a subject would broaden the scope as subjects are general in nature.