An IT manager in the aviation sector checks the industry's threat intelligence feed to keep up on the latest threats and ensure the work center implements the best practices in the field. What type of threat intelligence source is the IT manager most likely accessing?

A$.$ Open Source Intelligence $($OSINT$)$

B$.$ An Information Sharing and Analysis Center $($ISAC$)$

C$.$ A vendor website, such as Microsoft's Security Intelligence blog

D$.$ A closed or proprietary threat intelligence platform