Which two objects are required to successfully create a TriggerSend object?

NTO is using a mobile campaign to collect an email addresses of interested subscribers. Using AMPscript’s API functions they will send a confirmation email when an email is texted into their short code .

Which two objects are required to successfully create a TriggerSend object? Choose 2
A . Attribute
B. TriggerSendDefinition
C. Contact
D. Subscribers

Answer: A,C