Please provide a detailed explanation to the following question and explain why the other answer choices are wrong.

[1] Which of the following documents provides the most persuasive evidence about the existence of a receivable? A. A credit approval document supported by the customer's audited financial statements. B. A copy of a sales invoice to the customer in the auditee's records. C. A positive confirmation received directly from the customer. D. A customer's purchase order in the auditee's records related to the credit sale