Final answer:
The correct format for importing a list into Marketo is a Comma separated values text document (CSV). This format is widely supported and easy to parse for systems like Marketo.
Step-by-step explanation:
The correct format to import a list into Marketo is D. Comma separated values text document. Marketo supports data import in the CSV format, as this is a universally accepted text format that separates values using commas, making it easy for systems to parse and import data.
It is important to ensure that the CSV file adheres to the specified criteria that Marketo requires for smooth data import, such as correct headers and data formatting.