What is the first thing the developer should check?

A developer identified a use case where a triggered send of an email is needed. The developer already successfully set up authentication with a Client ID and Client Secret has used them in several REST calls. When the REST call is made, a "401 Unauthorized" error is returned.

What is the first thing the developer should check?
A . The send permissions have been granted for the Client ID and Client Secret within Installed Packages.
B. The email interaction has been started
C. The automation permissions have been granted for the Client ID and Client Secret within Installed Packages.
D. The email interaction has been published.

Answer: A