An investment firm's ESG integration approach is most likely outlined in its ESG policy. This document provides a detailed framework of how the firm incorporates ESG factors into its investment process.

ESG policy (A): This policy typically includes the firm's principles, strategies, and methodologies for integrating ESG factors into investment decisions. It outlines the firm's commitment to ESG considerations and provides guidance on how these factors are incorporated at different stages of the investment process.

Statement of Investment Principles (B): This document may include high-level investment principles, but it does not specifically focus on the detailed ESG integration approach.

Corporate social responsibility report (C): This report highlights the firm's CSR activities and impacts but is not focused on the investment process itself.