Choice "D" is correct. Selecting a sample of vendors' invoices for comparison to receiving reports is performed during fieldwork. This is not part of the planning phase.
Choice "b" is incorrect. Coordinating the assistance of entity personnel in data preparation is usually performed during the planning phase.
Choice "c" is incorrect. During the planning phase, matters that may affect the audit should be discussed with firm personnel responsible for non-audit services to the entity.
Choice "a" is incorrect. During the planning phase, the auditor generally would read the current year's interim financial statements.