How could the developer validate if the email was successfully sent?

A developer uses the messageDefinitionSends REST API endpoint to send a triggered send email. This method returns a 202 (success) response code.

How could the developer validate if the email was successfully sent?
A . Use the messageDefinitionSend/key:(key)/deliveryRecords REST endpoint with GET method
B. The 202 response code indicates the message was sent successfully; no further action is required.
C. Use the validateEmail REST resource with POST method to obtain the email delivery details from the request.
D. Confirm the record was successfully inserted into the associated Triggered Send Data Extension.

Answer: A