Question

a ______ is a type of research method used in scientific investigation to understand situations. case study interview interdependent variable trophic level

Explanation:

A case - study is a well - known research method in scientific investigation to understand specific situations in depth. Interviews are also research methods but less fitting here compared to case - study. Interdependent variable is not a research method. Trophic level is related to ecology and not a research method.

Answer:

A. Case Study