Answer: C) first-hand ethnographic fieldwork
Explanation: Primary research strategies are methods use to aquire first hand (primary) data directly from the research/study (inhabitants) arear rather than making use of secondary source of data.
The kind of study Maria wants to undergo will require her to get her data directly from the women in the coffee field because an in-depth analysis will be needed.
So Maria will likely use first-hand ethnographic fieldwork strategy (participant observation) to gain a holistic perspective in order to answer her research questions.