Final answer:
The marketer should examine the C. 'Unsubscribed Leads' smart list to find which records have opted out of emails, since this list contains the leads that have chosen not to receive marketing emails.
Step-by-step explanation:
To identify which records have opted out of receiving emails, a marketer should look at the system smart list labeled as Unsubscribed Leads. This smart list will give them information on all leads that have explicitly indicated they no longer wish to receive marketing emails. Often, email marketing systems and customer relationship management (CRM) platforms have a method of tracking these preferences to ensure compliance with email marketing laws and regulations, like the CAN-SPAM Act.
Blacklists are typically lists of email addresses that have been marked due to spam or abusive behavior and are therefore blocked from receiving any communications. The Marketing Suspended list would include leads that the marketer has paused from receiving communications for various reasons that may not necessarily pertain to the lead's preference, such as for quality assurance or while updating data. The No Acquisition Program list refers to leads that were not acquired through a specific marketing program or campaign.
Therefore, the correct answer is C. Unsubscribed Leads, as it directly relates to the leads that have chosen to opt-out of receiving marketing emails.