What setting must be enabled to confirm who submitted a communication log form entry?

To confirm who submitted a communication log form entry, the correct setting to enable is to keep the "Collect email addresses" option checked. This setting ensures that the form will automatically gather the email address of each respondent who submits an entry. By having their email address attached to their responses, you can easily identify who made each submission, which is especially useful for maintaining a record of communications or tracking responses for administrative purposes.

While the other options may contribute to form functionality or tracking in different contexts, they do not specifically address the need to identify the individual submitter. For instance, the requirement for sign-in could help restrict access to specific users, but it may not collect email addresses from everyone, particularly if external users are involved. Similarly, the response receipt feature allows respondents to receive a confirmation of their submission but does not inherently identify who submitted the form. Lastly, setting up a notification system for entries serves as a method to alert the form creator about new submissions but does not facilitate identifying individual respondents. Therefore, the most direct approach to confirming the identity of form submitters lies in collecting their email addresses.