C
Below is a question with multiple-choice answers. Choose the correct option based on your reasoning.

### Question:
What would be the best way to determine the role of squirrels in a forest ecosystem?

### Choices:
A. measure the length and mass of several squirrels
B. determine the genes that control squirrel traits
C. make field observations of squirrels in their natural habitat
D. read articles about the energy and nutrient requirements of squirrels

### Answer:
