An internal auditor concluded that delays in an ongoing construction project have cost the organization...

Comprehensive and Detailed Explanation:

Audit conclusions must be backed by sufficient, relevant, and reliable evidence (Standard 2330). In construction audits, the most reliable evidence of cost overruns and delays comes from payment records and milestone documentation (A), which clearly show the financial impact tied to project performance. While photos (B) may illustrate delays, they are not sufficient proof of cost impact. Sprint planning (C) is not relevant to construction projects and does not provide financial evidence. Internal rate of return (D) is a performance metric, not evidence of actual cost overruns. Therefore, the appropriate evidence for workpapers must be the payment and work milestone documents that support the $10 million loss conclusion.