A step-by-step explanation of what the authors did in detail.

The correct answer is "Methods". In a research paper or article, the methods section typically describes the specific procedures and techniques used by the authors to conduct their study or experiment. This section provides a step-by-step explanation of what the authors did in detail, including the materials used, data collection methods, and statistical analysis. It is an essential part of the paper as it allows other researchers to replicate the study and assess the validity and reliability of the findings.