Final answer:
The statement about 'unreasonable delays by management' is most likely sourced from observation during audit fieldwork, as this reflects a typical concern auditors note while gathering evidence on-site.
Step-by-step explanation:
The most likely source of the statement 'There were unreasonable delays by management in permitting the commencement of the audit and in providing needed information' is d. Observation during audit fieldwork. During an audit, auditors will perform fieldwork where they directly observe and gather evidence regarding the practices and operations of the entity being audited.
This statement reflects a typical concern that might be noted during such fieldwork, as it directly pertains to the auditors' ability to perform their work timely and effectively.
In contrast, a management representation letter is a statement from management confirming certain aspects of the audit, an inquiry with external legal counsel would involve legal matters of the entity, and a management inquiry is a dialogue with management regarding operations, not typically a source to document delays.