Final answer:
The step key to avoiding irrelevant literature in a Related Literature Review is 'Defining the scope of the review,' ensuring the research focuses on pertinent studies.
Step-by-step explanation:
The essential step in writing the Related Literature Review (RRL) of your research study to avoid large, irrelevant literature, would be c) Defining the scope of the review. This step ensures that the literature included in the review is directly relevant to the research topic. By setting clear boundaries for the review, the researcher can focus on material that directly pertains to the research questions or hypotheses and filter out extraneous information. This helps maintain clarity and ensures the research stays on track, thereby avoiding an unnecessary bulk of unrelated literature that would not contribute to the study's aims.