1) The auditor must gather sufficient and appropriate evidence during the course of the audit. Sufficient evidence must: （ ）
选项：

A:A) be well documented and cross-referenced in the audit documents.;
B:B) be based on sources that are external to company.;
C:C) provide evidence that prove or disprove an audit objective/assertion.;
D:D) be persuasive enough to enable the auditor to issue an audit report.