What is a language format designed to exchange threat intelligence that can be transported over the TAXII protocol?

What is a language format designed to exchange threat intelligence that can be transported over the TAXII protocol?
A . STIX
B . XMPP
C . pxGrid
D . SMTP

Answer: A

Explanation:

TAXII (Trusted Automated Exchange of Indicator Information) is a standard that provides a transport mechanism (data exchange) of cyber threat intelligence information in STIX (Structured Threat Information eXpression) format. In other words, TAXII servers can be used to author and exchange STIX documents among participants.

STIX (Structured Threat Information eXpression) is a standardized language which has been developed in a collaborative way in order to represent structured information about cyber threats. It has been developed so it can be shared, stored, and otherwise used in a consistent manner that facilitates automation and human assisted analysis.