After Ann, a user, logs into her banking websites she has access to her financial institution
mortgage, credit card, and brokerage websites as well. Which of the following is being described?

A.
Trusted OS

B.
Mandatory access control

C.
Separation of duties

D.
Single sign-on

Explanation:
Single sign-on means that once a user (or other subject) is authenticated into a realm, reauthentication is not required for access to resources on any realm entity. The question states that
when Ann logs into her banking websites she has access to her financial institution mortgage,
credit card, and brokerage websites as well. This describes an SSO scenario.