Which configuration is recommended for the re-engagement email send?

A customer would like to send a quarterly re-engagement email to subscribers who have not opened in the previous three months.

The customer’s plans are to:

* Use an existing Paste HTML email for the first send.

* Make only minor changes to the email creative for future sends.

* Use an existing Measure to build the subscriber audience for current and future sends.

* Deploy emails manually for now, but possibly automate in the future.

Which configuration is recommended for the re-engagement email send?
A . Triggered Send
B . Guided Send
C . Automated Send
D . User-Initiated Send