What type of single Sign-on is this?

Universal containers (UC) has implemented SAML -based single Sign-on for their salesforce application. UC is using pingfederate as the Identity provider. To access salesforce, Users usually navigate to a bookmarked link to my domain URL .

What type of single Sign-on is this?
A . Sp-Initiated
B . IDP-initiated with deep linking
C . IDP-initiated
D . Web server flow.

Answer: A