Which send method should be used?

A customer wants to send a quarterly reengagement 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.

• Send to the subscriber list.

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

Which send method should be used?
A . Guided Send
B . Triggered Send
C . Send Flow Activity
D . Send Email Activity